Hatching and larval development of the semiterrestrial tropical brachyuran Sesarma angustipes were studied in relation to salinity in laboratory experiments. Adults were found in southern Brazil living in terrestrial habitats and in freshwater creeks. When a free choice was offered in the laboratory, females liberated their larvae indiscriminately in freshwater or seawater. Rearing experiments were carried out at 0, 3, 10, 20, and 32% S. Unlike in other marine and brackish water species, freshly hatched zoea I larvae remained actively swimming in freshwater, where they survived for almost 2 d. Maximum survival time of zoea I exposed to 3% S was ca 3.5 d. The larvae were able to pass through some or all developmental instars (4 zoeal stages and 1 megalopa) only at higher salinities.