Bothered by the injury in the third and fourth sets, the top-seeded Sampras battled through the pain to defeat a stubborn Karol Kucera of Slovakia, 7-6 (11-9), 3-6, 6-3, 6-4.
After the match, Sampras went to a hospital to undergo an MRI, which will determine his status for a third-round match with fellow American Justin Gimelstob, who defeated Frenchman Michael Llodra, 7-6 (7-3), 6-3, 6-4.
Women's top seed Martina Hingis of Switzerland got off to a slow start in her second-round match with 78th-ranked Jing-Qian Yi of China. But the world No. 1 stormed through the second set in 21 minutes to record a 6-4, 6-1 victory.
Martina Navratilova, who Hingis is named after, was victorious in her return to the All-England Club after a five-year absence.
The 43-year-old Navratilova and South African Mariaan de Swardt struggled past Lubomira Bacheva of Bulgaria and Amanda Hopmans of the Netherlands, 6-3, 6-7 (4-7), 6-3, in a first-round doubles match.
Sampras had his hands full with Kucera, a former top-10 player who knocked off Andre Agassi in the second round at the French Open.
After staving off two set points in the first-set tiebreaker, Sampras found himself down a break at 1-3 in the second before breaking back in the next game. But the Slovakian broke for a 5-3 lead and served out the set to level the match.
Kucera was unable to carry that momentum over to the third set as Sampras stormed out to a 5-2 advantage. But the tide of the match seemed to swing over to Kucera's side as Sampras called an injury timeout after the seventh game to receive treatment on his left shin.
Reminiscent of his epic U.S. Open quarterfinal match against Alex Corretja in 1996 when he vomited on the court, Sampras' suffering was evident as he barely made an effort to chase down shots. But like he did in New York four years ago, Sampras did just enough to pull out the win.
After managing to serve out the third set, Sampras gamely fought on in the fourth as he broke Kucera for a 4-3 advantage. With darkness falling on Centre Court, Sampras struggled to put away Kucera while serving for the match at 5-4.
Sampras committed three double faults in the 10th game, the last of which gave Kucera a break opportunity. But the Slovakian was unable to capitalize as Sampras served his 12th ace of the match. Sampras fired two straight service winners to seal his sixth win in seven meetings with Kucera and improve to 48-1 in his last 49 matches at Wimbledon.
French Open runner-up Magnus Norman of Sweden could not translate his claycourt success at Roland Garros to the grass at the All-England Club. The third seed was stunned by 19-year-old Belgian qualifier Olivier Rochus, 6-4, 2-6, 6-4, 6-7 (4-7), 6-1.
In other upsets, Belarussian qualifier Vladimir Voltchkov eliminated 1997 runner-up and sixth seed Cedric Pioline of France, 6-3, 6-3, 2-6, 3-6, 6-4, and Wayne Ferreira of South Africa surprised 1996 champion Richard Krajicek of the Netherlands, the 11th seed, 5-7, 6-3, 6-3, 7-6 (7-3).
Ninth seed Thomas Enqvist of Sweden managed to reach the third round as he got past Francisco Clavet of Spain, 7-6 (7-2), 7-6 (8-6), 7-5.
Two days after stopping a 21-match losing streak by eliminating local favorite Greg Rusedski, American Vincent Spadea was defeated by Spain's Albert Portas, 6-4, 6-3, 6-3.
Another American coming off an impressive win was Jan-Michael Gambill, who defeated Fabrice Santoro of France, 4-6, 6-4, 6-2, 6-2. Gambill knocked off seventh seed Lleyton Hewitt of Australia on Wednesday.
American Justin Gimelstob will be Sampras' third-round opponent after beating Michael Llodra of France, 7-6 (7-3), 6-3, 6-4.
On the women's side, French Open finalist Conchita Martinez of Spain, the fourth seed and 1994 champion, was stunned by 79th-ranked Sonya Jeyaseelan of Canada, 6-4, 6-1, in just over an hour. This was Martinez's earliest Wimbledon exit since falling in the second round in her debut in 1992.
On the other hand, sisters Venus and Serena Williams had no trouble winning their second-round matches. Seeded fifth, Venus Williams dumped Ai Sugiyama of Japan, 6-1, 6-4, and Serena Williams, seeded eighth, crushed Yvette Basting of the Netherlands, 6-1, 6-0, in only 33 minutes.
The reigning U.S. Open champion needed just 33 minutes to dispatch the 186th-ranked Basting, who managed only four points in a second set which lasted only 12 minutes. One of those points was a double fault by Williams.
"My opponent tried her best and you can't ask for more than that," Serena Williams said. "At least it (second set) gave me an opportunity to start coming into the net and close out points that way."
After missing last year's event with the flu, the 18-year-old Serena Williams repeated her 1998 run as she secured her place in the third round.
Germany's Anke Huber, the 11th seed, needed three sets to get past Britain's Louise Latimer, 5-7, 6-3, 6-3. Huber, who overcame eight double faults and 33 unforced errors, had 32 winners.
Russia's Anna Kournikova, a semifinalist three years ago, was dismissed by Anne-Gaelle Sidot of France, 6-3, 6-4. Still seeking her first career title, Kournikova suffered her earliest exit from Wimbledon in three appearances.