Gustavo Kuerten was the defending champion, and successfully defended his title against Àlex Corretja in the final 6–7(3–7), 7–5, 6–2, 6–0.
Martina Navratilova was the defending champion, but she was defeated by Hana Mandlíková in the final, 7–6(7–3), 1–6, 7–6(7–2).
Cara Black and Liezel Huber were the defending champions, but lost in the quarterfinals to sisters Alona Bondarenko and Kateryna Bondarenko.
Richard Krajicek was the defending champion, but lost in the semifinals to Jan Siemerink.
Andriy Medvedev was the defending champion but lost in the second round to Jordi Burillo.
The 1999 Sydney International – Women's Singles was the singles event of the fourteenth edition of the ASB Classic; a WTA Tier II tournament and the second most prestigious women's tennis tournament held in Australia. Arantxa Sánchez Vicario was the defending champion but lost in the quarterfinals to Barbara Schett.
The 1999 Evert Cup – Singles was the singles event of the eleventh edition of the tennis tournament played at Indian Wells, California, United States. It is the second WTA Tier I tournament of the year, and part of the US Spring tennis season. World No. 1 Martina Hingis was the defending champion but lost in the quarterfinals to Chanda Rubin.
The 1999 Bausch & Lomb Championships – Singles was the singles event of the twentieth edition of the Bausch & Lomb Championships; a WTA Tier II tournament held in Amelia Island, Florida, United States, played on green clay. Mary Pierce was the defending champion but lost in the quarterfinals to Conchita Martínez.
Michael Chang was the defending champion but lost in the second round to Pete Sampras.
Marat Safin was the defending champion and won in the final 3–6, 6–3, 6–3 against Rainer Schüttler.
Roger Federer was the defending champion and successfully defended his title, becoming the first player since Andre Agassi in 1996 to do so. He defeated Mardy Fish in the final 6–7(5–7), 7–6(7–1), 6–4. It was his fourth win at the event; he also won in 2005, 2007 and 2009. It was also Federer's 17th Masters tournament win putting him level with Agassi and his 63rd career title overall, equalling Björn Borg.
Manon Bollegraf and Rick Leach were the defending champions but lost in the first round to Lindsay Davenport and Jan-Michael Gambill.
Yevgeny Kafelnikov was the defending champion and defended his title with 6–4, 6–4 against Magnus Larsson.
The 1999 WTA German Open – Singles was the singles event of the fifty-fifth edition of the tennis tournament played at Berlin, Germany, the most prestigious tennis tournament in Central Europe. It was the sixth WTA Tier I tournament of the year, and part of the European claycourt season. Conchita Martínez as the defending champion; Martínez lost in the third round to Arantxa Sánchez Vicario.
Andrea Hlaváčková and Lucie Hradecká were the defending champions, but lost in the semifinals to Maria Kirilenko and Nadia Petrova.
Sara Errani and Roberta Vinci won the tournament by defeating Maria Kirilenko and Nadia Petrova 4–6, 6–4, 6–2 in the final.
The 1999 Eurotel Slovak Open – Singles was the tennis singles event of the first edition of the most prestigious tournament in Slovakia. In a final of two future World No. 1s, Amélie Mauresmo defeated Kim Clijsters in straight sets, 6–3, 6–3.
Roberta Vinci was the defending champion, but lost in the quarterfinals to unseeded Kristina Mladenovic.
Martin Kližan was the defending champion, but lost in the quarterfinals to Tomáš Berdych.
Elitsa Kostova was the defending champion from the event's previous edition as an ITF Women's Circuit tournament, but lost in the first round of qualifying to Barbora Štefková.
Frances Tiafoe was the defending champion, but lost in the first round to Dan Evans.
