Survival of 12.7 g (average body weight) Litopenaeus vannamei was examined at temperatures of 14, 16, 18, 28, 32, 34 and 36$^{circ}C$ and salinities of l0, 20, 30 and 40 ppt after 7 days. Hemolymph osmolality was measured at 12 combinations of salinities (l0, 20, 30 and 40 ppt) and temperature levels (18, 28 and 34$^{circ}C$) after 14 days. The results show that the species have their best survival between temperatures of 18 and 3$0^{circ}C$ and salinity above 20 ppt. Hemolymph osmolality increased with increased salinity at all temperatures tested. The isosmotic point calculated from the linear relationship between hemolymph osmolality and medium osmolality and recorded as 826, 809 and 1,117 mOsm/kg which is equivalent to 29.4, 28.8 and 40.2 ppt at 18, 28 and 34$^{circ}C$, respectively. The slopes obtained from the relationship between hemolymph osmolality and medium osmolality were 0.314, 0.276 and 0.541 for L. vannamei at 18, 28 and 34$^{circ}C$, respectively, suggesting that the shrimp at 34$^{circ}C$ regulated osmotic concentration much worse than those at 18 and 28$^{circ}C$. This result also indicated that L. vannamei living at 34$^{circ}C$, showed more fluctuation in hemolymph osmolality than those at 18 and 28$^{circ}C$.