The influence of exercise on hormonal and total white blood cells (WBC), lymphocytes (L). Granulocytes (GR), and platelet (P) count responses was studied in: twenty-five patients with chronic airway obstruction (CAO, 47 +/- 1.8 years, mean +/- SEM) and thirteen normal subjects (N, 36 +/- 2.6 years). They performed a submaximal (40 W) and a maximal exercise (VO2max). Arterial blood samples were taken at rest, 40 W, and VO2max. [H+], PaCO2, PaO2 haematocrit (Hct), [Hb], P, total platelet volume (TPV), WBC, GR, L, and total red blood cells (RBC) were measured. At rest, WBC, GR, P and TPV were higher in CAO patients, whilst PaO2 and cortisol were lower. At 40 W, when compared to values obtained at rest, WBC, GR, L, P and TPV were increased in both groups; WBC, GR, P and TPV were higher in CAO patients. VO2max of CAO patients represented 54% of that of controls. At VO2max, Hct, [Hb] and RBC were approximately 10% higher than at rest in both groups, whilst changes were more significant in normals for WBC (CAO = 55%, N = 76%), lymphocytes (CAO = 83%, N = 105%), GR, (CAO = 37%; N = 51%), platelets (CAO = 23%, N = 29%), TPV (CAO = 25.4%, N = 35%), [H+] (CAO = 43%, N = 38%) and ACTH (CAO = 82%, N = 139%). PaO2 and cortisol did not differ between groups. PaCO2 and platelets however, were higher in the CAO group.(ABSTRACT TRUNCATED AT 250 WORDS)