The aim of our study was to investigate the efficacy of pramipexole in advanced parkinsonian patients by means of an acute stimulation test. We studied the motor effects of pramipexole in fluctuating parkinsonian patients by comparing the response to acute levodopa with the response to levodopa + pramipexole. The adjunct of pramipexole to levodopa increased the time spent on from 136 +/- 22.3 to 186 +/- 20.6 minutes (p<0.01), while it did not change the latency to on, the magnitude of the motor improvement, or the duration and severity of dyskinesias. The main effect of pramipexole in fluctuating parkinsonian patients is an increased duration of the on phase.