Blood was collected from 486 feral horses of mixed sex and age classes captured from three wild horse management areas in Nevada and Oregon from December 1985 to February 1986. Males were significantly outnumbered by females in the Flanigan area, but both sexes were represented in approximately equal numbers in the Wassuk and Beaty's Butte areas. Hematology and chemistry values averaged 16.4 ± 0.11, 46.3 ± 0.28, 9.9 ± 0.07, 6.9 ± 0.10, 47.1 ± 0.24, 16.6 ± 0.09, 35.2 ± 0.09, 10.4 ± 0.14 and 23.4 ± 0.25 for hemoglobin (HGB), hematocrit (HCT), red blood cells (RBC), white blood cells (WBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), Cortisol (F) and serum urea nitrogen (SUN), respectively. Statistically significant differences in HGB, HCT, RBC, WBC, MCV and MCH levels occurred with respect to age (P ≤ 0.001). Serum F levels were lower in immature animals than in either subadult or adults in all areas. Flanigan horses appeared in the poorest condition and had the lowest HGB, HCT and RBC counts while the values for Wassuk horses were significantly higher (P ≤ 0.001). Serum F levels were lowest in the Flanigan horses. A significantly lower (P ≤ 0.001) proportion of adult mares had progesterone levels consistent with pregnancy in the Flanigan horses versus those from the other two areas. These data are consistent with a subjective evaluation of the condition of the horses.