Top seed Rafael Nadal made an impressive start to the final pre-French Open event with a 6-1 6-0 win over Bosnia's Damir Dzumhur in Rome.
The 31-year-old, whose 21-match unbeaten run on clay ended last week, had a first-round bye and will play Denis Shapovalov or Robin Haase next.
Elsewhere, Fabio Fognini was roared to victory by a partisan Italian crowd as he upset sixth seed Dominic Thiem.
Great Britain's Kyle Edmund plays France's Lucas Pouille after 18:00 BST.
Former world number one Novak Djokovic - who has sunk to a ranking of 18th after six defeats in his 12 tour matches this year - eased past Georgia's Nikoloz Basilashvili 6-4 6-2.