Synopsis Feeding lindane, in capsule form, to laying hens at a rate equivalent to 100 mg/kg food for 1 or 2 weeks had little effect on egg production. Longer periods of feeding resulted in a 20 to 30% decrease in the rate of egg production. When treatment was stopped after 4 weeks, the birds recovered and egg production returned to its original rate within a month. The production of flocks treated for 6 weeks or longer became permanently depressed since some birds went out of lay and failed to resume production when the treatment was terminated. Egg shell thickness, egg and yolk weight and hatchability were not significantly affected by the treatment.