Perhaps the most universal problem in many of Kentucky's streams, from the angler's viewpoint, is that of excessive numbers of rough fish in proportion to the numbers of game fish. This paper presents the findings of a Dingell-Johnson project that has been concerned since 1952 with the manipulation of populations in 3 streams typical of types found in the state. The upper 46 miles of North Fork River in Mason County and 12 miles of Whippoorwill Creek in Logan County were treated with 5-percent powdered rotenone in 1952 to eradicate their entire fish populations. Both streams were immediately restocked with game and panfish species. Annual sampling of the population of both streams revealed a gradual reversion to the original population composition in each stream. It was concluded that total population manipulation could be accomplished, and at no more prohibitive cost than other comparable management techniques, but that any benefit to the game fish species was of questionable value and of short duration. Similar findings resulted from removing undesirable species from U.S miles of Floyd's Fork Creek (Bullitt County) with an electric seine during 1955. All available evidence indicates that partial or total population manipulation alone (without environmental alteration or improvement) holds little promise as a management tool for improving tpe population composition of the average Kentucky stream.