The effect of electrostatic field treatment of the testis on the offspring of male rats was investigated. The results showed that treatment ranging from 1 to 7 kV caused reduced fertility, but no deaths occurred among the treated animals during the experiment. Observations at 3, 30, 60 and 90 days after exposure showed no recovery of fertility among the treated rats. Treatment with 6 or 7 kV caused congenital anomalies in the offspring, such as micropthalmy, elongation of the foreskin of the penis (praeputium-like), 'rounded face' with omnidirectional hair growth, and narrow pelvis in adult female offspring. The anomalies might be caused by changes to the genetic material in the sperm. The sex ratio of offspring in the experimental groups was not significantly different from normal, suggesting that the number of male and female offspring was unaffected by treatment. The number of offspring with experimentally linked congenital anomalies decreased with time.