By means of a T-test, I compared the estimated ranges of those 48 mice following their fourth capture with ranges estimated after the fifth capture. The results did not demonstrate significant differences between the two sets of estimates; therefore, I decided to use data resulting from four or more captures, and at three or more stations. Table 3 shows estimations of the home ranges of males and females of each species of _Peromyscus_. When the inclusive boundary-strip method is used, the area encompassed by the range tends to be larger than the area of the same range when estimated by the exclusive boundary-strip method. Stickel (1954:4) has shown that the inclusive boundary-strip method overestimates the home range by about 17 percent. Analysis of Home Range by Inclusive Boundary-Strip Method When all age groups were considered, the ranges of 16 males of _P. truei_ averaged 20,000 to 80,000 square feet (ave. 47,333; S. D. 19,286). The sizes of home ranges were not significantly different (P > 0.05) between adult and subadult (including juveniles and young) males. All females of _P. truei_ (22) had ranges encompassing 16,666 to 83,333 square feet (ave. 40,666; S. D. 17,566). Sizes of home ranges between adult and non-adult females did not differ significantly. The mean range of adult males of _P. truei_ did not differ from that of adult females (P > 0.05). Fifteen males of _P. maniculatus_ had ranges of 16,666 to 66,666 square feet (ave. 34,222; S. D. 16,000); six adult males had ranges of 33,333 to 53,333 square feet (ave. 38,666). Sizes of home ranges of adult and non-adult males of this species did not differ significantly. Five females of _P. maniculatus_ had ranges of 33,333 to 76,666 square feet (ave. 51,333; S. D. 15,913); of these, four adults had ranges of 33,333 to 53,333 square feet (ave. 45,000). Sizes of home ranges of adult males of this species did not differ (P > 0.05) from those of adult females. The ranges of adult males of _P. truei_ were compared with ranges of adult male of _P. maniculatus_; likewise the ranges of adult females of each species were compared. In each case no difference was demonstrable in sizes of ranges between the species. The largest home range of any _P. truei_ was that of animal number 18, a young male with an estimated home range of 133,333 square feet. This animal was caught only five times, and his home range appeared unusually large in relation to that of other young males of this species; hence some of the widely-spaced sites of capture probably represent excursions from the animal's center of activity, rather than the true periphery of his range. These data were, therefore, not used in further computations. Stickel (1954:13) pointed out the advisability of removing such records from data to be used in calculations of home range.