The follow-up of 42 patients affected by lupus membranous nephropathy (LMN) is reported and compared with that of 43 patients affected by diffuse proliferative lupus glomerulonephritis (DPGN), who were the object of a previous study. According to the WHO classification, the patients were subdivided into two groups: pure LMN (Va + Vb class) and LMN with superimposed proliferative lesions (Vc + Vd class). Antiphospholipid antibodies (APA) and lupus anticoagulant were tested in 23 subjects. All the patients were treated with corticosteroids, which were associated to cytotoxic drugs in 28 cases. Although a higher number of complete remissions was obtained in patients with pure LMN, the difference between the 2 groups was not significant (7/26 vs 1/16). At 10 years kidney survival was 93% in all LMN patients with no significant differences between the 2 groups. This 10-year kidney survival rate is very similar to that previously observed by us for DPGN (91%). The WHO histological classification and the chronicity index did not identify the patients who reach end-stage renal failure. Eight patients suffered from thrombotic manifestations which were the cause of death in two cases. Fourteen of the 20 patients studied presented echocardiographic abnormalities. A statistically significant association was found between the occurrence of cardiovascular complications and APA levels. The effectiveness of treatment in LMN remains controversial. We suggest, however, that adequate therapy may significantly improve the prognosis of lupus nephritis thus reducing the differences in the outcome of SLE patients having different histological WHO classes. Cardiovascular illness represents a frequent and severe late complication.