The RQ values for the TGF-ß1, SMAD3, and ILK genes, as well as miR-21, in ectopic tissue were analyzed in relation to the clinical features of patients with endometriosis: age at the time of diagnosis, stage of endometriosis (according to rASRM classifications), pelvic pain symptoms (according to the numerical rating scale–NRS), phase of the menstrual cycle, and concentrations of the biochemical parameters of CA-125 and HE4. Here, SMAD3 is linked to endometriosis.