Prepubertal pigs (N = 6) were surgically implanted with iv and intracerebroventricular catheters. The animals were given oCRH or hCRH peripherally (0, 20 or 50 micrograms) or centrally (0, 10 or 20 micrograms) and the effect on plasma cortisol measured. Peak cortisol concentrations were observed 20 min after iv, and 40 min after intracerebroventricular, administration. A larger cortisol response was observed when 20 micrograms oCRH was given by the central, compared to the peripheral, route and intracerebroventricular administration of both 10 and 20 micrograms oCRH caused excitation and vocalisation. By contrast, the effect of hCRH on cortisol secretion was small, regardless of the route of administration, and only one animal displayed a behavioural response when the highest dose was given centrally.