The effects of levodopa on tests measuring auditory and visual perception, auditory, and visual short-term memory, verbal learning, and on attention and concentration were studied in 29 patients with Parkinsonism. Thirty-two control subjects matched with the Parkinsonism patients on age, educational level, and verbal IQ were administered the same tests to control for practice effects. Significant improvement occurred for the Parkinsonism patients in verbal learning (an intermediate memory test) and in auditory perception. These improvements were unrelated to changes in anticholinergic medications, increases in alertness or concentration, lessening of depression, or improved motor ability or control. There was no test evidence of levodopa improving visual perception, short-term auditory or visual memory, alertness or concentration. Thus, there is no objective test evidence for levodopa producing a generalized awakening or an alerting effect in Parkinsonism patients who are intellectually alert and well-orientated. Interpretation of the test findings suggests a specific awakening effect, that of improvement in intermediate memory but not in short-term memory. Overall, the Parkinsonism group scored below the control group on all tests, suggesting that cognitive impairment accompanies Parkinson's disease even in patients who are intellectually intact and well oriented.