In discussing the extremes in sex ratios which can be tolerated among pheasants, the author reviews spring sex ratio data obtained from other Michigan pheasant studies, and discusses results obtained from expts. conducted to determine the extreme spring sex ratio which can be tolerated among pheasants without reducing the productivity of the species. Conclusions reached in the report indicate that a low population of cocks in spring does not necessarily mean that an unusually large number of hens will go unmated, or that an excess of infertile eggs will be produced. The expt. indicated that the mating of a cock pheasant to a hen may be effective for an average of 22 days ranging from 11 to 42 days. The number of eggs produced during the time when sperms were effective ranged from 3 to 35, averaging 16, and of all eggs produced 77% were fertile. These data combined with the facts that cocks are highly polygamous and their mating season is long, provide a good basis for assuming that a spring sex ratio of one cock per 10 or 12 hens is not out of proportion. The author concludes that on areas where the pheasant population approaches the carrying capacity, a divergence in sex ratio might conceivably result in increased production.