Twenty right-handed patients affected by early/mild Parkinson's disease were evaluated in a randomised study using neuropsychological and clinical assessements during three treatment modalities: when in the off treatment condition, when on pramipexole, and when on l-dopa. In comparison to the off treatment condition, the DA-agonist pramipexole produced a significant impairment of short term verbal memory, attentional-executive functions and verbal fluency, while l-dopa did not. Moreover, pramipexole opposite to l-dopa, failed to improve FAS and Stroop tests. Present findings indicate that pramipexole may worsen cognitive functions although not exceeding normative values.