Venus Williams played her first WTA match in studded Sony Ericsson Open.
The seven-time Grand Slam titlist Williams returned with a victory by handling 41-year-old Japanese Kimiko Date-Krumm, 6-0, 6-3. The lopsided match was over in 77 minutes.
The veteran Date-Krumm was a Miami runner-up 17 years ago.
Williams had been sidelined since pulling out of her second-round match at last year's U.S. Open. The American star has been battling Sjogren's syndrome, an incurable autoimmune disease that causes fatigue and joint pain.
The former world No. 1 Williams' second-round opponent on Friday will be Wimbledon champ Petra Kvitova.
Williams owns three titles at this event (1998-99, 2001) and was a runner-up on another occasion.
Clijsters, meanwhile, also shook off some rust in fighting from behind to beat capable Aussie Jarmila Gajdosova, 4-6, 6-1, 6-0, on the hardcourts at the Tennis Center at Crandon Park.
The four-time major champion Clijsters' second-round opponent will be 14th- seeded German Julia Goerges, who was one of 32 seeds to receive an opening- round bye.
Clijsters, sidelined by some nagging injuries since late January, was a Miami champion in 2005 and 2010.
American qualifier Sloane Stephens fought back to beat France's Pauline Parmentier 4-6, 7-6 (7-4), 6-4, while Czech veteran Iveta Benesova dismissed Russian Elena Vesnina 7-6 (7-5), 6-1, and Swede Sofia Arvidsson handled Argentine Gisela Dulko 6-4, 7-5 on Day 2.
Other Day-2 winners were French qualifier Stephanie Foretz Gacon, Czech Barbora Zahlavova Strycova, Russian qualifier Valeria Savinykh, Hungarian Melinda Czink, and Israeli Shahar Peer, who should have her hands full with former world No. 1 Maria Sharapova in the second round. Zahlavova is rewarded with a second-round match against former No. 1 Caroline Wozniacki, while Savinykh will take on U.S. Open champion Samantha Stosur.
The top seed here is also the defending champion, Victoria Azarenka, who is fresh off her title at Indian Wells last week. The current world No. 1 star and Australian Open titlist from Belarus is off to a perfect 23-0 start this season.
Azarenka, who also titled in Miami in 2009, topped the three-time Sony Ericsson Open runner-up Sharapova in last week's finale at Indian Wells and last year's title tilt at Crandon Park.
The potent field here features yet another former No. 1 in Serena Williams, who is a five-time Miami champ (2002-04, 2007-08) and two-time runner-up.
The winner of the $4.828 million tournament will collect $712,000.