Since the Sony Ericsson WTA Tour Rankings was introduced on November 3, 1975, 19 women have occupied the No.1 spot in singles. Six of those ascended to No.1 in doubles at some point in their careers, and five of those occupied the No.1 position in singles and doubles simultaneously for a period.

Some former singles No.1s do not have illustrious histories on the doubles court, but that does not mean they lacked the skills for it. For instance, Steffi Graf possessed an impressive 173-72 match record in doubles - a 71% winning percentage - and surely would have won more than 11 titles had she played more often. Same with Chris Evert, who only won eight doubles titles, but had a 117-39 match record - a 75% winning percentage.

Below is a look at the doubles highlights of all 19 singles No.1s in Tour history.

Austin, Tracy
Doubles Highlights: titles - 4; career-high ranking - No.41
Notes: All four of her titles came alongside Betty Stove.

Capriati, Jennifer
Doubles Highlights: titles - 1; career-high ranking - No.28
Notes: Her lone title came alongside Monica Seles at Rome in 1990.

Clijsters, Kim
Doubles Highlights: titles - 11 (2 Grand Slams); career-high ranking - No.1
Notes: Seven of her titles came alongside Ai Sugiyama … She achieved her career-high singles ranking of No.1 one week after reaching her career-high doubles ranking … Her three total weeks being simultaneously ranked No.1 in singles and doubles is tied for fourth-most in history … Both of her majors came in 2003 - at Roland Garros and Wimbledon.

Davenport, Lindsay
Doubles Highlights: titles - 37 (3 Grand Slams); career-high ranking - No.1
Notes: Her three majors came with three different partners … Won the Tour Championships three straight years ('96-'98) with three different partners … Her three total weeks being simultaneously ranked No.1 in singles and doubles is tied for fourth-most in history.

Evert, Chris
Doubles Highlights: titles: 8 (3 Grand Slams); career-high ranking - No.13
Notes: Three of her eight titles, two of which were majors, came alongside singles rival Martina Navratilova.

Goolagong Cawley, Evonne
Doubles Highlights: titles - 11 (5 Grand Slams); career-high ranking - No.1
Notes: Three of her majors came alongside Peggy Michel … Four of her Grand Slam titles came at the Australian Open.

Graf, Steffi
Doubles Highlights: titles - 11 (1 Grand Slam); career-high ranking - No.3
Notes: Her one major - Wimbledon in 1988 - occurred the same year she won the Golden Slam in singles (all four Grand Slams, plus the Olympic gold medal) … Four of her titles came alongside Gabriela Sabatini, including her lone major.

Henin, Justine
Doubles Highlights: titles - 2; career-high ranking - No.23
Notes: One of her titles and her lone runner-up finish came alongside Meghann Shaughnessy.

Hingis, Martina
Doubles Highlights: titles - 37 (9 Grand Slams); career-high ranking - No.1
Notes: She won 11 titles alongside Anna Kournikova, including two Grand Slams and two Tour Championships … Four of her majors came at the Australian Open … She was the fourth woman in history to record a calendar-year doubles Grand Slam with her victories at all four majors in 1998 … Her 29 total weeks being simultaneously ranked No.1 in singles and doubles is second-most in history.

Ivanovic, Ana
Doubles Highlights: titles - 0; career-high ranking - No.50
Notes: Her best finish at a Tour event is a runner-up showing at 's-Hertogenbosch in 2006 alongside Maria Kirilenko.

Jankovic, Jelena
Doubles Highlights: titles - 1; career-high ranking - No.43
Notes: She captured her lone title at Birmingham in 2006 alongside Li Na.

Mauresmo, Amélie
Doubles Highlights: titles - 3; career-high ranking - No.29
Notes: Two of her titles have come alongside Svetlana Kuznetsova, with whom she also has had her best Grand Slam finish - runner-up at Wimbledon in 2005.

Navratilova, Martina
Doubles Highlights: titles: 177 (31 Grand Slams); career-high ranking - No.1
Notes: Her 177 doubles titles is the most all-time for a male or female … She is one of three women to win the singles, doubles and mixed doubles at the same Grand Slam, which she accomplished at the 1987 US Open … She won the singles and doubles at the same Tour event a record 84 times … Her 103 total weeks being simultaneously ranked No.1 in singles and doubles is a record … Her 109-match doubles win streak alongside Pam Shriver is a record … Won Tour Doubles Team of the Year a record eight straight times with Shriver, with whom she captured 79 titles, 20 of which were majors … Her Grand Slam haul consisted of eight Australian Opens, seven French Opens, seven Wimbledons and nine US Opens … She won the Tour Championships 11 times.

Safina, Dinara
Doubles Highlights: titles - 8 (1 Grand Slam); career-high ranking - No.8
Notes: Her eight titles have come with seven different partners, with Katarina Srebotnik the one player with whom she has won twice … Her lone major came at the 2007 US Open alongside Nathalie Dechy.

Sánchez-Vicario, Arantxa
Doubles Highlights: titles - 69 (6 Grand Slams); career-high ranking - No.1
Notes: Three of her majors occurred at the Australian Open … Fifteen of her titles, including three of her Grand Slams and one Tour Championships, came alongside Jana Novotna … Eleven of her titles, including two of her Grand Slams and one Tour Championships, came alongside Helena Sukova … Her seven total weeks being simultaneously ranked No.1 in singles and doubles is third-most in history.

Seles, Monica
Doubles Highlights: titles - 6; career-high ranking - No.16
Notes: Her six titles came alongside six different partners.

Sharapova, Maria
Doubles Highlights: titles - 3; career-high ranking - No.41
Notes: Two of her titles have come alongside Tamarine Tanasugarn.

Williams, Serena
Doubles Highlights: titles - 17 (10 Grand Slams); career-high ranking - No.3
Notes: Her Grand Slam haul consists of three Australian Opens, one French Open, four Wimbledons and two US Opens … She won Olympic gold medals alongside sister Venus in 2000 and 2008 … She has only played without Venus twice, winning a title one of those times alongside Alexandra Stevenson at Leipzig in 2002.

Williams, Venus
Doubles Highlights: titles - 16 (10 Grand Slams); career-high ranking - No.3
Notes: Her Grand Slam haul consists of three Australian Opens, one French Open, four Wimbledons and two US Opens … She won Olympic gold medals alongside sister Serena in 2000 and 2008 … All her titles have come alongside Serena and she has only played four tournaments with anyone else.