<p justify;"="" style="text-align: justify;">Acute toxicity test (96hr.) was carried out to determine the toxic effects of the organochlorine pesticides and heavy metals on larvae of crab Macrophthalmus erato. The 96hr. LC 50 values were 0.48,3.2,90.0 and 152.0 pg/L of endosulfan, HCH, copper and zinc respectively for the first zoeal stage. The order of toxicity to the larvae was Endosulfan > HCH > Copper > Zinc. The calculated safe concentrations were 0.0048,0.032, 0.900 and 1.52 pg/L for endosulfan, HCH, copper and zinc respectively.