Body size and condition of coyotes (Canis latrans) from a high-density population in Webb County, Texas (USA) were analyzed for age, sex and seasonal differences during 1980 to 1986. Mean body mass was progressively greater for juvenile, yearling and adult coyotes. Males were heavier and longer than females in each age class. Indices of intraperitoneal fat deposits were similar between sexes. Juveniles continued growth from fall to spring. Adults and yearlings both lost intraperitoneal fat overwinter. Mean body mass of adults decreased overwinter but mass of yearlings did not differ significantly between fall and spring. Territorial and transient female coyotes did not differ in mean body mass, length or indices of subcutaneous fat deposits.