It is widely appreciated that patients with systemic lupus erythematosus (SLE) get thinner and shorter hair. However little work has been done to quantitate this. We assessed hair thickness of SLE patients and compared this to that of patients with rheumatoid arthritis (RA) and healthy controls (HC). Fifty-seven female patients with SLE (mean age: 32 +/- 8 years) and 77 female patients with RA (mean age: 50 +/- 12 years) were studied along with 75 healthy women (mean age: 27 +/- 6 years). Five strands of hair were taken from each subset and mounted on glass slides. Two independent observers, blind to the sources of the hair, measured the hair strands under a light microscope, using a micrometer. Finally, the mean hair thickness between each of the three groups was calculated. The hair in both SLE and RA patients was found to be thinner than that of HC by both observers (P +/- 0.001). Age adjusted analysis between SLE and HC showed similar results. However, there was no significant difference in hair thickness between SLE and RA. SLE patients have thinner hair compared to HC. More studies are needed to investigate the effect of disease activity, therapy and other factors on hair diameter.