A one-dimensional paper chromatographic method is presented for determination of urinary homovanillic acid. The method is faster and gives higher values than does two-dimensional chromatography. Urinary homovanillic acid values are given for patients with metastatic malignant melanoma and for presumed normals. Homovanillic acid level was elevated in the case of amelanotic melanoma. Determinations of urinary homovanillic acid may be a valuable adjunct to the therapy and study of metastatic malignant melanoma.