The occurrence of nephritis is considered to be the most important factor influencing the prognosis in systemic lupus erythematosus (SLE). Despite the apparent histological similarity of the lesions, however, patients with diffuse proliferative glomerulonephritis (DPGN) may exhibit different outcomes. A retrospective study was carried out on 81 SLE patients with DPGN to evaluate the prognostic significance of different clinical, serological and histological variables; in particular, 95 renal biopsies were re-evaluated and the activity and chronicity indices for the patients were determined. A positive correlation was observed between the presence of chronic lesions on renal biopsy and a poor renal outcome (< 0.001). Moreover, in the repeat biopsies the patients with a poor outcome showed a higher degree of chronic lesions. Active lesions and other clinical and serological parameters did not correlate with the outcome.