Sex ratios are of primary importance in interpretation of extensive studies of pheasant populations. They are necessary for converting crowing-cock indices to population estimates even where annual trends are to be studied in the same area. Reliability of population estimates from hunting season kill of pheasants suffers primarily from inability to estimate sex ratios accurately. Fall sex ratio is an index to production and where adult sex ratios are divergent can serve as a good check on production per hen. Age ratios of cocks cannot be interpreted directly as an index of productivity, even within the boundaries of one state, unless adult sex ratios are known. The relationship between observed and actual sex ratio varies significantly from season to season and according to the method of observation. In view of their importance in population studies and the lack of reliability of present methods, it is believed that intensive studies on techniques for obtaining sex ratios are a major need in pheasant research.