Penaeus monodon postlarvae (PL1, PL5, PL10, and PL15) and juveniles (0.2 and 2 g mean weights) were acclimated gradually within 6 h to test temperatures of 22°, 28°, and 33°C. After 24 h, the postlarvae were abruptly transferred to salinity levels of 8, 16, 24, 32, 40, or 50 ppt, and juveniles to 0, 4, 8, 16, 20, 24, 28, 32, 40, 50, or 60 ppt. All test animals were previously reared in 32 ppt sea water at a temperature of 27-29°C. Survival rates were compared after four days for PL1, PL5, and PL 10, and 10 days for PL 15. Tests for juveniles lasted seven days. Length and total (TPI) or mean (MSI) population stage indices were compared for postlarvae. Survival rates of postlarvae and juveniles were generally lower at 33°C. Length and MSI of postlarvae were higher at 33°C than at 22°C. TPI at PL10 and PL15 were not significantly affected by salinity. Optimal salinity ranges for postlarvae and juveniles were identified based on the different parameters measured.