This report explores the effects of dw on early growth rate as well as adult body size in populations produced during the transfer of dw from an egg-type (Leghorn) to broiler-type populations. This sex-linked gene, dw, was observed to have the following effects when compared with those of its normal, dw+, allele:Eight week body weight of heterozygous, dw+dw, sons from normal, dw+, dams was equal to that of their normal homozygous, dw+dw+ sons. In contrast, eight-week body weight of dw+dw sons from dwarf dams may have been slightly suppressed when compared with dw+dw+ sons of normal dams.In the hemizygous females, the smaller egg size from the dw dam reduced the eight week weight of her dwarf (dw) but not her normal (dw+) daughters. As the amount of broiler-type inheritance was increased through backcrossing to transfer dw from the egg-type to broiler-type populations, the depressing effect on dw on growth of females was reduced from 37.1 to 19.2% at eight weeks of age and from 29.4 to 19.8% at 26 weeks after hatching. The effect of dw on adult size, as estimated by shank length, did not appear to diminish after the first back-cross to broiler-type dams.