In earlier studies (Bridges & Jones, 1967, 1968) we found a significant relationship between adrenocortical responses to the psychological stress of an oral university examination (2nd M.B. Anatomy examination) and body-build, assessed by means of phenotyping by the method of Parnell (1958). This assumes three basic components of physique: fatness (F), muscularity (M) and linearity (L). It was found that the mean plasma corticosteroid concentration at the time of the examination was significantly greater in the primarily linear group than in the mainly muscular students, and there was a significant negative correlation between the examination corticosteroid values and the muscularity scores (r = − 0·225; P < 0·05). One explanation for these findings would be that the muscular group was characterized by a lower sensitivity of adrenocortical response. It was decided to test this possibility using the methods of Landon, James, Wharton & Friedman (1967).