The objective of this study was to establish reference hematologic and biochemistry values for adult riparian brush rabbits (Sylvilagus bachmani riparius). Between February 2002 and December 2003, complete blood cell counts and serum biochemistry panels were done on blood samples collected for 252 healthy, adult riparian brush rabbits that were bred in captivity and released to the wild in the California, USA, San Joaquin Valley. Significant differences in mean values of some analytes were found among males, nonpregnant females, and pregnant females and among seasons. However, when reference values for each subgroup (sex, pregnancy status, and season) were compared with reference values for all riparian rabbits combined, differences were not sufficiently relevant clinically to warrant the adoption of separate subgroup-specific reference values. The reference ranges reported herein will be of value to veterinarians and wildlife biologists assessing the health of riparian brush rabbits and other wild Sylvilagus species.