Systemic lupus erythematosus (SLE) is a rare disease in males. There is evidence that a functional state of hypoandrogenism is important in the pathogenesis of the disease. We analysed the levels of several hormones (follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), estradiol (E2), free estradiol (FE2) and prolactin (PRL)) in 17 male SLE patients and 17 male healthy controls with similar age distribution. Three lupus patients were excluded from the analysis due to previous cyclophosphamide therapy or pre-puberty. Thus 14 male lupus patients were eligible for the study. Six of the 14 SLE patients (43%) showed at least one abnormal level of FSH, LH or T. There were no abnormalities in these hormones in the 17 controls. This difference was significant (P < 0.01). In five of these 6 male patients (36% of all lupus patients) the hormonal profile was compatible with a functional state of hypoandrogenism (high LH and/or low T). The ratio E2/T (estradiol/testosterone:pmol/nmol) was also significantly higher in the SLE group (average = 6.5; SD 4.3) when compared with that of the control group (average 4.2; SD 1.2; Mann-Whitney rank sum test: P < 0.03). There were no significant differences in E2, FE2 or PRL between lupus patients and controls. We did not confirm the notion that left-handedness is frequent in male lupus as all our patients were right-handed. We found a significantly higher prevalence of sex hormone abnormalities in male lupus patients when compared with healthy controls with a similar age distribution.(ABSTRACT TRUNCATED AT 250 WORDS)