The use of L-dopa and carbidopa in metastatic malignant melanoma. A combination of L-dopa and carbidopa was given orally to 17 patients with metastatic melanoma. Maximum tolerated oral doses were given, up to 4 grams daily. No response was seen in 15 patients evaluable for response. Toxicity was considerable, with seven of 17 patients (41%) stopping treatment because of unacceptable gastrointestinal toxicity or postural hypotension. Contrary to previous anecdotal reports, there was no evidence that L-dopa/carbidopa treatment resulted in accelerated progression of metastatic melanoma. Orally administered L-dopa/carbidopa is ineffective as therapy for advanced melanoma when maximum tolerated doses are used. 