Some aspects of the biology of the sea cucumber Holothuria scabra Jaeger, 1935 were studied along the coast of Dar es Salaam. Samples of H. scabra were collected from Kunduchi and Buyuni between January and December 1999. The abundance of Holothuria scabra was higher in Buyuni (3951) than in Kunduchi (1176). However, the level of exploitation per year from far reefs was higher in Kunduchi than in Buyuni. Sea cucumber harvesting by villagers is done monthly on intertidal areas and from reef flats near to the villages. Higher catches from Buyuni were recorded during August and November (perhaps due to light winds such that trips could be made to far-off reefs), while the catch from Kunduchi was relatively low throughout a year. The length-frequency distribution of H. scabra was found to be unimodal, with most individuals ranging between 8.5 cm and 26.5 cm. The species showed continuous breeding with peaks between May and September and December. The average size at first maturity in H. scabra was 16.8 cm.