Using 60 hens reared and kept on a standard lighting programme (decreasing followed by increasing photoperiod to 22 weeks of age and 14 h continuous light: 10 h continuous dark during lay) as control, the effects of the following intermittent patterns on development and performance were studied. Group 1. The same rearing programme, followed by, between 20 and 36 weeks, 3 h light (L):3 h dark (D) intermittent and then from 36 weeks a regime in which each light period was progressively shortened by 30 min every 8 weeks with corresponding lengthening of the dark period so that the last cycle used between 52 and 60 weeks was 1.5 h L:4.5 h D. Group 2.6-hour light-dark cycles from hatching; the light:dark ratio first decreasing and then increasing, such that total light hours per day varied as in the control group to 20 weeks, and then subsequent lighting as in 1. Group 3. Intermittent lighting of 1.5 h L:4.5 h D unvaryingly from 4 to 60 weeks. Sexual development was essentially the same in all groups. Egg numbers were decreased slightly by the short light-dark cycles but daily egg mass output was the same in all groups. Food utilisation was best in group 1 and worst in the control group. In general egg weight and shell quality were improved by the short light-dark cycles; the effect appearing with the first eggs and being especially marked for group 3. On intermittent regimes ovipositions were equally distributed, between the four daily light-dark periods when the light:dark ratio was near unity but were more numerous during the first half of the solar day when the ratio was 1.5 L:4.5 D.