The relative amount of FN-fibrin I complex was at a similar level in endometriosis (29.75 ± 6.88%) and fertility disorders (30.20 ± 5.58%), and was significantly higher (p < 0.00002 and p < 00006) in relation to the normal group (12.95 ± 15.75%). The gene discussed is FN1; the disease is endometriosis.