Dysarthria is a common manifestation in patients with idiopathic Parkinson's disease. This study investigated the effects of levodopa on intelligibility in patients with Parkinson's disease. Ten participants were tested during on- and off-states using the Yorkston and Beukelman intelligibility test (1980). Intelligibility as scored by a panel of speech therapists was significantly improved in the on-condition. No correlation was found, however, between intelligibility and overall severity of the disease or severity of the motor problems.