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Rough-toothed dolphins (Steno bredanensis) were sighted 145 times from 1 September 1995 through 22 March 2000 off La Gomera, Canary Islands. Sightings were made during regular whale watching trips and occurred year-round. Group size ranged from 1 to 50 individuals (mean 16.8, SD=12.0, n=137). Mean depth was 506 m (range 20-2500, SD=473 m, n=140) and mean distance from shore was 4.44 km (range 0.05-14.8, SD=2.33 km, n=137). Behavioural data, collected for 26 sightings showed that the reaction of the animals to the observation vessel varied from no response to interaction. Boatrelated behaviours were quantified and were rare up to frequent per sighting, with approaches (46%), bowriding (21%), and scouting (20%) being the predominant types of behaviours. Interactions between the dolphins and swimmers also differed in their duration and intensity. The year-round abundance off La Gomera indicated that this species might endure temperatures well below 25°C. Moreover, for the first time, behavioural categories were defined for the rough-toothed dolphin.