Swimming was observed in specimens of the dromiid crab Homola barbota collected at Naples, and the swimming technique was studied by the analysis of cine film. The first, second and third walking legs beat in the frontal plane of the crab. The duration of the backward propulsive stroke is the same as that of the forward recovery stroke. The legs of each side beat in the sequence 3-2-1, with a lag of about one-third of a cycle between successive legs. The opposite legs of a pair beat about half a cycle out of phase. The form of the leg movement in forward and sideways swimming was observed. The function of the swimming is probably to escape from benthic predators.