To study the effects of endosulfan, a mild estrogen-mimic,on survival, growth and reproduction of the model zebrafish Danio rerio, the hatchlings were discretely immersed at selected doses (44–1400 ng/l) for 14 h. Immersion at the dose of 350 ng/l resulted in 12 and 27% mortality at the end of the treatment and at the age of sexual maturity respectively, as well as in the production of 72% females. The frequency of ‘juveniles' increased from 17% at 44 ng/l to 44% at 1400 ng/l. Endosulfan acted as a growth suppressant and the magnitude of its suppression increased in the order of female > male > juveniles.