Physiological measurements of two indigenous zebu breeds of cattle, Bunaji (BU) and Sokoto Gudali (SG) and the half-crosses of Friesian-White Fulani (CB) were taken after exposure under field conditions. Observations were made over a period of four months, two of which were during the cool season and two during the hot season. Rectal temperature (RT) did not differ between breeds but respiration rate (RR) and sweating rate (SR) were higher in the CB. Haematocrit (HT) and plasma protean (PP) did not differ significantly between breeds. The repeatability of RR was moderately high, both within and between seasons. RR is therefore a more reliable physiological measure of response to climatic stress. The CB is less adapted than the zebu.