South African pace bowler Charl Willoughby took two wickets in five balls to give Somerset the edge of a rain-hit first day in their Championship First Division match at the Rose Bowl.
Willoughby dismissed Chris Benham with the first ball of the 45th over and then induced Nic Pothas to drive a catch in the covers to Alfonso Thomas.
Hampshire ended the day 113 for 4, with rain driving the players from the field for the last time after one ball of the 51st over. At that stage Michael Lumb was unbeaten with 49 and teenager Liam Dawson had scored five.
Hampshire captain Dimitri Mascarenhas chose to bat first on a slow wicket when play got under way two-and-a-half hours late and with 24 overs wiped from the day's allocation.
Somerset were without their captain Justin Langer – who was ruled out by a back injury – and were led instead by former England bowler Andrew Caddick.
The visitors drafted in batsman Arul Suppiah in place of Langer, while Hampshire gave opportunities to James Adams and England Under-19 all-rounder Dawson.
Paul Terry, who is standing down as manager of Hampshire at the end of the season, was again absent for the third successive time, leaving his assistant Giles White to take charge of the team.
Adams and Michael Carberry put on 47 for the first wicket in 18 overs before Carberry, who had made 18, was adjudged to have been leg before wicket to Peter Trego.
Trego struck again at 60 in the 26th over when a slower delivery deceived Adams and lured him into offering a return catch, which the bowler held one-handed.
Lumb and Benham took the score to 93 before Willoughby made his contribution. Benham had scored 15 when he got an inside edge and the normally reliable Pothas followed at the same score to leave Hampshire reeling.