Recent reports on the use of a quantitative measurement of S100B protein for the detection of metastatic melanoma have yielded promising results. In this study we evaluated 489 serum samples from 64 patients suffering from advanced melanoma (UICC/AJCC stage IV) to compare the sensitivity of a S100B immunoradiometric assay (IRMA) with that of conventional blood parameters as well as other known clinical prognostic factors. In a univariate statistical analysis, gender, bone metastasis, and lactate dehydrogenase and S100B levels in serum samples were found to be significant prognostic markers (P < 0.05). The S100B level represented the only relevant independent prognostic marker that was sustained in a multivariate analysis (P = 0.016). Furthermore, we were able to demonstrate that S100B is of relevance irrespective of the specific sites of metastatic involvement. The other laboratory parameters could not match the sensitivity rate of S100B. Overall survival rate was strongly associated with serum S100B values. The results of our study suggest that S100B might be a useful tool as a melanoma marker and an independent prognostic factor in advanced metastatic melanoma. S100B serum detection is likely to be of great interest for the pretreatment stratification and/or monitoring of patients enrolled in clinical studies.