Results of recent studies have indicated that the amount of edge habitat in an area may be an important factor in determining home range size of pumas. We tested this hypothesis with data on home ranges of pumas in southern Idaho/northwestern Utah. The study area is highly fragmented into forest patches and sagebrush open areas. We tested three predictions: (1) the percent of edge would be negatively related to home range size, (2) the amount of edge habitat in the home ranges of pumas would be similar, regardless of the size of the home range and (3) there would be more edge habitat within home range boundaries than in general areas of similar size. Home range size (90%) varied from 29.8 to 118.7 km². The percent of edge within home ranges was negatively correlated with home range size (F  =  22.3, P < 0.001, R²  =  0.53), but amount of edge habitat within the home ranges was not. The mean percent of edge within home range boundaries (16.0 ± 1.4 (se) %) was significantly greater (t  =  2.88, P  =  0.006) than general areas of similar size (11.3 ± 1.2%). We concluded that the amount of edge within an area was influencing the size of home ranges. We proposed that pumas needed a certain minimum amount of edge (hunting habitat) to successfully hunt their prey and that the amount of “catchable” prey was more important than just general prey abundance.