Family and twin studies have shown that heritability accounts for endometriosis development to an extent similar to other complex genetic diseases. Both linkage analysis and association studies have been performed to identify genetic determinants for the disease. Results from the linkage scan of 1,176 families collected thanks to a joint effort between an Australian and a UK group supported significant linkage to a novel susceptibility locus on chromosome 10q26. Although gene variants with effects on the disease predisposition have been proposed to exist and several candidates have been put forward, their effects have not been or are yet to be confirmed. The main categories of candidate genes studied have been those involved in detoxification processes, sex steroid biosynthesis and action, immune system regulation. Genetic studies on endometriosis face numerous challenges as the disease has several manifestations and different forms. Moreover, strong gene-environmental interactions might definitively influence approaches to identify genetic variants involved. Genome-wide association studies that survey most of the genome for causal genetic variants provide the potential for future progress.