A 4 x 2 factorial experiment was carried out to evaluate the effects of four supplementary light intensity levels in Combination with two sex ratios on the productive and reproductive performance of Domyati ducks. Eighteen-week-old, 552 Domyati ducks (456 duck hens and 96 drakes) were randomly distributed into 8 groups; four of which had a sex ratio of611 while the other four groups had a sex ratio of 4:1 (duck henszdrake) of three replicates each, housed separately in floor pens and exposed to a daily photoperiod of 17 hours up to the end of the experiment at 60 weeks of age. To maintain this daily 17-hour photoperiod thr0ughout the experimental period from 20 to 60 weeks of age, the length of natural day light was supplemented with artificial light, providing light intensity levels of 1 5 (served as a control), 10, 45 or 90 lux at birds' head level of the four experimental groups within each sex ratio respectively. The criteria of response were laying performance (age at sexual maturity, total eggs number, laying rate%, egg weight, egg mass, feed consumption and feed conversion), eggs fertility and hatchabiiity percentages, some egg quality traits (egg weight, shell weight, albumen weight, yolk weight, shell thickness and egg shape index), some morphological measurements on reproductive organs (testicular, ovarian and oviduct weights and oviduct length), and concentrations of some blood constituents (total protein, albumin and globulin), and gonadotrophic hormones (Ll and FSH). Significant differences were observed in total eggs number, laying rate %, egg mass, feed intake and feed conversion; but were not observed in age at sexual maturity or egg weight, due to the effects of supplementary light intensity level or sex ratio, in favor of the 10—lux supplementary light intensity and 6:1 sex ratio Eggs fertility and hatchabiiity were significantly improved by exposing ducks with 6'1 sex ratio to the 10-lux supplementary light intensity, and no further improvement was achieved upon subjecting the ducks to 45 or 90 lux. With the exception of a higher oviduct weight achieved wrth the 6.1 sex ratio neither supplementary light intensity level nor sex ratio affected significantly the testicular and ovarian weight or the oviduct length. Egg quality was not significantly influenced by either supplementary light intensity level or sex ratio, except that a higher eggshell weight was achieved by the exposure ofducks to supplementary light intensity levels of 10, 45 or 90 lux. Significant differences were detected only in levels of blood plasma total protein and globulin; in males at 40 weeks of age and in females at 60 weeks of age, due to the effect of supplementary light intensiity level. Significant supplementary light intensity level by sex ratio interactions were found only for total eggs number, laying rate %, egg mass and feed conversion whereas their effects were not interrelated for the other criteria.