A prospective pilot study on radioimmunoscintigraphy with monoclonal antibody fragments against cutaneous melanoma (MoAb 225.28S) was carried out in 17 patients with a clinical diagnosis of choroidal melanoma. Monoclonal antibodies against melanoma-associated antigen were labeled with 740 mBq 99mTc and injected IV; images were made with a gamma camera at 6 h after injection. With a double-pinhole collimator, radioactivity was counted thrice in both eyes at 6 h after injection. In 6 of 16 patients (37.5%), the melanoma could be imaged with the gamma camera. With the double-pinhole collimator, a significantly higher activity was measured in the melanomatous eye in 13 of 16 patients (82.4%). In two patients a false negative result was obtained, and in one patient the difference between the left and right eye was not significant. Considering these results, radioimmunoscintigraphy may be valuable in ocular melanoma diagnostics, but the specificity of MoAb 225.28S needs to be assessed.