We evaluated the influence of the hereditary make-up on the development of systemic lupus erythematosus (SLE) in two ethnic groups [Gypsy and white Caucasian Mediterranean (WCM) populations], living in the same geographic area. We compared 81 WCM and 25 Gypsy patients with SLE. The control group consisted of 185 healthy unrelated individuals, 105 WC and 80 Gypsies. In the Gypsy population, the onset of SLE occurred at earlier ages than in the other ethnic group (25.9 versus 32.0 years, P = 0.02), and showed lower SLEDAI peak values (4.9 versus 7.0, P = 0.016). The frequency of joint, kidney, gastrointestinal and eye involvement was significantly lower in Gypsy patients. In contrast, SLE-associated antiphospholipid syndrome, thrombosis and livedo reticularis were more frequent in Gypsies than in the majority ethnic group (WCM). In WCM patients, DRB1*1303- DQB1*0301 haplotype was associated with SLE ( P = 0.001, Pc = 0.038). We found SLE to be associated with DR5 ( P = 0.006, Pc = 0.05) in the Gypsy population as well as a protective effect of DPB1*0401 when DR5 was not present ( P = 0.008, Pc = 0.032). In conclusion, we found some clinical differences between WCM and Gypsy patients with SLE. Furthermore, HLA associations between HLA-DRB1-DQB1 and SLE were different for Gypsy people.