Larvae of Metapenaeus monoceros (Fabricius) at protozoea 1 (PZ1) stage were stocked in 2-L glass flasks to investigate the effects of various salinities (25, 30, 35, 40, 45, 50 and 55 ppt) on growth and survival until the post-larval (PL) stages. The PZ larvae were not able to tolerate a sudden salinity drop of over 10 ppt. Yet, an abrupt salinity increase of over 10 or even 15 ppt did not cause mortality. The PZ larvae were successfully acclimated to different test salinities at a rate of 4 ppt h(-1). The larvae displayed better tolerance to high rather than low salinities. The lowest and highest critical salinities appeared to be 22 and 55 ppt respectively. Taking into account survival, growth and development results, the optimal salinity for the larval culture of M. monoceros inhabiting the Eastern Mediterranean was 40 ppt. At this salinity, the PZ1 larvae were successfully cultured until PL1 stage within 11 days with 68% survival on a feeding regime of Tetraselmis chuii Kylin (Butcher) (20 cells mu L-1), Chaetoceros calcitrans Paulsen (50 cells mu L-1), Isochrysis galbana Parke (30 cells muL(-1)) and five newly hatched Artemia nauplii mL(-1) from M1 onwards at 28 degreesC.