OBJECTIVE To characterize the course of lupus nephritis (LN) in terms of demographic indices (sex, age of renal disease onset), the presence of antiphospholipid syndrome (APS) and to ascertain a prognostic role of the disease exacerbations. METHODS A total of 121 LN patients were followed up from 1997 to 2004 (mean duration of the follow-up 5.6 +/- 6.4 years). A LN course was characterized by the presence of a complete or partial remission, exacerbation of the disease, repeated hospitalisations. Two types of exacerbations were considered: proteinuric, running with progressive proteinuria and normal renal function (type 1); functional, running with elevation of blood creatinine (type 2). RESULTS Exacerbations were observed in one third of the examinees, 70% of them ran with renal dysfunction. Exacerbations occurred more frequently in males than in females (50 vs 27%, respectively; p = 0.08) and in patients with early onset of LN (at the age of 40 years and younger, 80 vs 60%, respectively; p < 0.05). Exacerbations of type 2 occurred in males, in patients with early onset of renal damage and in APS association. It is shown that LN exacerbations, their incidence and type (a functional type) have a negative influence on renal survival of the patients. CONCLUSIONS Identification of groups of LN patients at high risk of exacerbations and unfavourable prognostic role of exacerbations dictates the necessity of due immunosuppressive therapy for maintenance of remission.