The most common types of levodopa-induced dyskinesias in patients with Parkinson's disease (PD) are chorea and dystonia, and often the two types are intermixed. Myoclonus is a far less common problem. The dyskinesias tend to develop over time, not usually being encountered at the initiation of levodopa therapy. Eventually, they affect more than 50% of patients on long-term levodopa treatment. Once they appear, they are difficult to eliminate. Substituting weaker dopaminergic agents for levodopa often fails to eliminate the dyskinesias. Most of the dyskinesias occur at the time of the highest brain concentration of levodopa and its product, dopamine--so-called peak-dose dyskinesias. Chorea and dystonia, usually in the legs, occur less commonly at the beginning and end of dosing, and these are called diphasic dyskinesias. Dystonia can also occur during the 'off' state, i.e. when the levodopa concentration is low. These 'off' dystonias are often painful and must be distinguished from peak-dose dystonia and from dystonia that may be a feature of PD itself.