The results of clinical double-blind trials using minoxidil 2% demonstrate the real efficacy of the drug in producing satisfactory esthetical results in some 30% of treated patients. One aspect of the results of this research which is not yet clear is the significant increase in the number of hairs, also found in voluntary subjects treated with placebo. In the present study is hypothesised that this increase may be partially explained by the failure to take into account the physiological seasonal variations in hair density, and by the confusion caused by the use of the "non-vello" category which is used to describe terminal (thick) and indeterminate (thin) hairs. In our study placebo failed to produce a significant increase in the number of terminal hairs, thus explaining why, even in the presence of an increased number of "non-vello" hairs, on average there was no real cosmetic benefit in these subjects