The offspring of pheasants (Phasianus colchicus) which were given 16 capsules once a week of lactose or combinations of lactose and 4, 6, or 10 mg technical grade dieldrin were placed in outdoor pens when 5 weeks of age. In July, August, October, December, and January, these young pheasants were caught by hand. They were more easily caught if both parents had received dieldrin, followed in order by those where hens only and cocks only had received dieldrin. In conducting studies of the effects of dieldrin on pheasants, we observed that chicks produced by parents given dieldrin appeared to be more readily caught by hand than those hatched from parents not given dieldrin. All of the chicks were then caught by hand several times over a 6nlonth period to document differences in susceptibility to capture. Baxter et al. (1969) reported that pheasant chick behavior in a visual cliff test was apparently affected by dieldrin given their parents. Effects of dieldrin on the relearning of visual discrimination and vigilance behavior by sheep have been reported by VanGelder et al. ( 1969). James and Davis ( 196S) reported DDT effects on discrimination ability of the bobwhite quail (Colinus vir. . gtnzanus . We are grateful to W. L. Tucker, South Dakota State University Agricultural Experiment Station Statistician, for his advice on data analysis. The South Dakota Cooperative Wildlife Research Unit is jointly supported by the South Dakota Department of Games, Fish and Parks, Bureau of Sport Fisheries and Wildlife, South Dakota State University and Wildlife Management Institute. METHODS AND PROCEDURES First generation stock used in this study vt7as purchased from South Dakota Pheasant Company, Canton, South Dakota, in the winter of 1969. Second generatioln birds were offspring we raised from birds purchased from Ringneck Ranch, Frederick, South Dakota, which were given capsules vv-eekly containing 0, 4, 6, or 10 mg dieldrin for 17 weeks from February-June, 1968. From February-June, 1969, all of these yearling birds were given 16 weekly doses of 0, 4, 6, or 10 mg dieldrin. Technical grade dieldrin (furnished by Shell Chemical Company) was administered with lactose in No. 5 gelatin capsules; pure lactose capsules were given to control birds. Based on average food consumption, a 6-mg capsule would correspond to approximately 20 ppm in the diet (Baxter et al. 19699. The general regimen of diet and care followed in this study was that described by Baxter et al. ( 1969 ) . Individually numbered eggs were incubated in pedigree cages; chicks were wing banded at hatching. Chicks used in this study were from 14 hatches betw7een April S-July 12, 1969. They were kept in brooders for 5 weeks and each weekly hatch was then placed outside in a 16x 16-ft pen. On July 14, lS, and 24, all the chicks in pens were caught for the first time. Chicks were again caught on August 18 and October 1. In December, birds were separated