The swimming behaviour and the sensory reactions of the blind Cuban cave fish Lucifuga subterranea Poey were studied on a single individual during a period of 6 months. Mechanical stimulation elicits but slight reactions. Gustatory substances in solution elicit fairly typical motor responses which are not followed by systematic exploration behaviour, the same being true for stimulations by odours of prey. The presence of moving prey provokes an oriented exploration with a slight plunging movement of the kind evidenced in other cave fishes. Actual seizing of the prey requires an active approach of the latter towards the anterior part of the body of the fish.