A total of 493 melanoma patients were investigated by 20 European nuclear medicine departments by means of the same 99mTc-labelled immunoradiopharmaceutical and the same immunoscintigraphy (ISG) protocol. (i) No chemical or clinical toxicity was detected during or following the studies. (ii) Positive results were obtained in 287/363 (79%) patients (321 carrying known lesions and 42 carrying previously occult lesions): in 231 (80%) of them, 402/402 lesions were imaged; in the remaining 56 ISG-positive patients, 108/204 lesions were imaged; in 76 patients 0/122 lesions were imaged. (iii) The fraction of melanoma lesions visualized by ISG was 510/728 (70.1%); 605 of these lesions were already documented at the time of the study, and 123 were previously occult. (iv) A total of 218 documented melanoma lesions (30%) were not visualized by ISG in 132 patients: about 70% of the ISG-negative lesions were of small size (less than 2 cm diameter). (v) The melanoma nature of 69/123 previously occult lesions was confirmed by clinical criteria and/or additional investigations in follow-up studies. The results obtained in this study are similar to those obtained in the Italian Multicentre Study which had previously been carried out with 258 melanoma patients.