Plasmatic proteasome (p-proteasome) has recently been described as a new marker for metastatic melanoma. The objective of this study was to compare the diagnostic and prognostic values of p-proteasome with three other melanoma serological markers: S100B protein, melanoma inhibitory activity protein (MIA) and lactate dehydrogenase (LDH) in the plasma of 121 stage I-IV melanoma patients. Laboratory analyses were performed by standardized ELISA (p-proteasome, MIA), immunoluminometric assay (S100B) and colorimetry (LDH). We found that all markers were relevant for discriminating metastatic from nonmetastatic patients but p-proteasome displayed the highest diagnostic accuracy. P-proteasome and S100B were the most sensitive (58.1%) and p-proteasome and MIA the most specific (98.7 and 100%) in detecting metastatic disease. P-proteasome and S100B had the highest area under receiver operating characteristics curve, 0.811 (95% CI: 0.725-0.897) and 0.822 (95% CI: 0.738-0.906), respectively. These two markers were the best in detecting patients with lymph node metastases. S100B, MIA and LDH diagnostic accuracy was increased when these markers were combined with p-proteasome. As shown with univariate analysis, shorter progression-free and overall survival rates were significantly associated with elevated plasma levels of each markers. The multivariate Cox regression analysis identified p-proteasome as the only independent predictor of a poorer progression-free survival (p = 0.030). In conclusion, this comparative study established that p-proteasome quantification in combination with other melanoma biomarkers is an attractive approach for the biological follow-up of melanoma patients.