The mean size of home range of 19 sea otters (8 females, 4 territorial males and 7 nonterritorial males) near Monterey, California, was 56 ha (range 18.3-198.2), with linear dimensions of about 2.5 .times. 0.3 km. Females had a significantly larger home range (80 ha, range 28.2-198.2) than territorial males (35 ha, range 18.3-57.8). Home ranges, as judged from data on the Monterey population, seem consistent with expected values for terrestrial croppers. The population showed distinct sexual segregation and many males exhibited territorial behavior.