Changes in sexual behaviour in patients with Parkinson's disease treated with levodopa are well recognized. Barbeau (1969) was the first to draw attention to “a clear-cut visually evident increase in libido” occurring in at least four out of 62 male parkinsonian patients treated with levodopa. Hyyppa et al (1970) reported that among 41 treated patients 10 experienced an increase of libido. De Ajuriaguerra et al (1972) reported that 29 out of 202 treated patients spontaneously told the authors of their satisfaction in respect of sexual behaviour. They commented “despite a few complaints from their spouses we do not believe there are any grounds to support the hypothesis of hypersexuality, but rather a more or less complete return to normal”. Similarly, Duvoisin and Yahr (1972) found that 8 per cent of a total of 283 patients reported an increase in sexual activity that “generally appeared to represent a partial return towards normalcy”. However, hypersexuality during levodopa therapy in parkinsonian patients was seen in senile dements, or as a feature of a more generalized disturbance, e.g. hypomanic behaviour. The subsequent experience of other authors (Bowers et al, 1971; Shapiro, 1973; Ballivet et al, 1973) has left no doubt that frankly hypersexual behaviour, albeit uncommon, may be provoked by levodopa treatment. Goodwin (1971) reviewed the literature on 908 patients and found an incidence of 0.9 per cent and Shapiro (1973) concurred, with an incidence in the region of 1 per cent of treated patients. Bowers et al (1971) reported 7 out of 19 patients on levodopa who indicated an activation of sexual behaviour on a combined scale of feeling and performance at some time during levodopa therapy. They divided the subjects into three groups: firstly patients who showed increased sexual drive apparently independent of motor improvement, secondly others whose sexual drive increased proportionately with their mobility, and thirdly those who developed hypersexual behaviour as part of an acute brain syndrome with an agitated and confused state.