Incidence of endometriosis is very high in women in the reproductive age (around 10%). To date, a reliable non-invasive diagnostic test for early diagnosis of endometriosis is not available. In this article we describe the potential value as diagnostic markers for endometriosis of two proteins (serum albumin and complement C3 precursor), previously identified as differentially expressed in women with endometriosis respect to healthy control by 2D gel analysis. A detailed description of the results obtained with this proteomic approach can be found in Signorile and Baldi . ELISAs were performed on a large cohort of endometriosis (n=100) and healthy patients (n=10) to establish the differential expression of the identified proteins. ROC analyses confirmed the statistical significance of the differential expression of these proteins: serum albumin (p=0.028) ad complement C3 precursor (p=0.082). Evaluation of these two proteins, together with the already described Zn-alpha2-glycoprotein , could help in the early identification of endometriosis patients.