Environmental chemicals with oestrogen-like activity are suspected aetiological factors of endometriosis. In animal experiments, cadmium was recently shown to possess oestrogen-like properties. In the frame of a case-control study designed to investigate environmental risk factors for endometriosis, we compared cadmium urinary excretion (CdU) and blood concentration in 59 patients with peritoneal endometriosis, deep endometriotic (adenomyotic) nodules of the recto-vaginal septum and controls. After standardisation for age (30 years) and smoking status, the mean levels of cadmium in urine were (geometric mean [geometric S.D.]) 0.25 [1.50], 0.29 [1.76] and 0.26 [1.46] microg/g creatinine, respectively. Cadmium concentrations in blood did not differ among the three groups. These data, therefore, do not support a role for cadmium in the onset or the growth of endometriosis or deep endometriotic (adenomyotic) nodules of the recto-vaginal septum.