Preliminary data on the applicability of salivary evaluations of testosterone (T), in comparison to plasma evaluations, in monitoring the effects of prednisone treatment in hirsutism are shown by the authors. 7.5 mg daily were administered p.o. to 4 volunteers affected by idiopathic hirsutism and to a fifth case in whom later surgery demonstrated the presence of adrenal virilizing tumour. While in the latter no modification either in plasma or salivary levels of the hormone was shown, in the four cases of idiopathic hirsutism a striking decrease of T levels was observed both in plasma (P less than 0.02) and in saliva (P less than 0.01). The two variations were moreover highly correlated (r = 0.80; P less than 0.001). Data obtained, although from a limited number of cases, seem then to confirm the validity of salivary T determination in this clinical condition, in whom the need of repeated evaluations, if performed on plasma, may become particularly stressful for the patient.