Top-seed Andy Murray made a solid start to his Rotterdam campaign with a 6-3, 6-2 win over French qualifier Nicolas Mahut.
The Australian Open runner-up, who played his first match since losing to Novak Djokovic in Melbourne, saved five of the six break points he faced.
Murray had a dip in concentration while serving for the match at 5-0, when Mahut finally broke him, but the 2009 champion held on his next service game.
Andrea Seppi also advanced to the second round with a 6-7, 6-3, 6-3 win over wild card Robin Haase to set up a match against defending champion Tomas Berdych.
Earlier, Sergiy Stakhovsky became the first player to seal his spot in the quarter-finals by defeating Dominic Thiem 6-1, 6-3.