This study evaluated the efficacy in Parkinson's disease (PD) of a new pharmacologic preparation of apomorphine included in microemulsions and administered by transdermal route, which provides a constant release of the drug for several hours (Apo-TD). Twenty-one PD patients with motor fluctuations were treated with L-dopa alone, with L-dopa plus oral dopamine-agonists, or with L-dopa plus Apo-TD. Apo-TD improved UPDRS-III and tapping test scores in "off" conditions, and reduced duration of "off" periods; no improvement in "on" conditions occurred. We conclude that Apo-TD shows its efficacy particularly by reducing "off" period duration and disability rather than improving motor performances in "on" conditions and therefore it seems a promising treatment for uncontrolled "off" phases in PD patients.