The plasma GH response to the L-dopa test (500 mg per os) has been assessed in 7 acromegalics who had never been treated before. Whereas three patients showed an increase in plasma GH, the other four presented a paradoxical response with a significant reduction in plasma GH levels. All subjects were put on to treatment with bromocryptin (10 mg/die). Three months later it was noted that only the four subjects with paradoxical response to L-dopa responded positively to bromocryptin treatment (at least 50% reduction in plasma GH). The L-dopa test was repeated in these four patients. In three of them who presented basal levels of GH lower than 10 ng/ml the L-dopa response curve was found to be reversed. It is concluded that in responsive patients, bromocryptin not only reduces GH levels but also normalizes the response to certain stimuli such as L-dopa.