In 1940 and 1941 records were maintained of animals trapped during predator-control operations in seven localities in New Mexico, Colorado and Wyoming. Traps were set for coyotes, Canis latrans, and bobcats, Lynx rufus, but such animals as badgers, Taxidea taxus, skunks, Mephitis mephitis, raccoons, Procyon lotor, and swift foxes, Vulpes velox, were unavoidably trapped. The studies were repeated in 1951 and again in 1960, and the catch-records are used to indicate the population levels of the commonly trapped carnivores at the three 9–11-year intervals. It is recognized that variations in numbers of these animals probably occurred annually and that the catch-records reported here serve only as rough indicators of population status or trends. In four areas in Colorado and New Mexico, coyote numbers declined from 1940–41 to 1951, then increased in 1960. The population trends of bobcats, skunks and raccoons were generally in the reverse direction, with the largest catches in 1951. Badgers and swift foxes continued to increase over the 20-year period. In the three Wyoming areas, the coyote population dropped in 1960 to 8 per cent of its 1940–41 level while numbers of the other carnivores increased sharply. More than 25 times as many bobcats, 3 times as many skunks, and 8 times as many badgers were caught in this state in 1960 as 20 years ago; 9 raccoons also were trapped in 1960 where none was taken in 1940–41. There were changes in the population levels of coyotes and of some or all of the other carnivores during each of the 10-year periods in each of the three states. The causes of the changes in the numbers of other carnivores are obscure, but it is evident in each case that the level of coyote control which was applied did not hold down the populations of these other animals.