The aim of this study was to evaluate 201Tl whole-body imaging in the detection of metastases prior to surgery in patients with malignant melanoma. Whole-body imaging was performed in 30 patients with known or suspected metastases 5 and 30 min after administration of 150 MBq 201Tl. The imaging results were compared with the histopathological findings in each patient on a lesion-by-lesion basis. Of the 39 metastases proven histopathologically, 34 were detected by 201Tl imaging (sensitivity = 87%), including 4 in-transit metastases and one inguinal lymph node metastasis which were unknown prior to investigation. Due to these additional findings on 201Tl imaging, scheduled surgical therapy was changed in three patients. 201Tl imaging was false-negative in four lymph node metastases and one skin lesion, and there were two false-positive 201Tl scans with tracer accumulation in inflammatory sites. The mean target-to-background ratio on the true-positive scans was 1.72 +/- 0.37 and 1.67 +/- 0.41 (P > 0.05) at 5 and 30 min post-injection respectively. In conclusion, 201Tl whole-body imaging appears sensitive and simple to perform in the detection of metastases prior to surgery in melanoma patients.