Renal biopsies of 86 patients with lupus nephritis were assessed according to the WHO classification, and according to activity and chronicity indices. The aim of the present study was to correlate clinical, and histological features (WHO class, activity and chronicity indices, and alpha-SM actin expression) with the progression of lupus nephritis, and identify the pathological role of alpha-SM actin in lupus nephritis. The median follow-up time was 75.5 +/- 57.3 months. Two patients were grouped as WHO class IIa lupus nephritis, eight patients as class IIb, 16 patients as class III, 25 patients as class IV, 15 patients as class V, and 19 patients as mixed pattern lupus nephritis. Sex, age, race, and the alpha-SM actin expression in glomeruli and tubulo-interstitial area in WHO class III and IV showed no correlation with clinical follow-up outcome of lupus nephritis. Unfavorable clinical outcome of lupus nephritis was correlated with WHO class IV compared to the other classes, and with the chronicity index in WHO class III patients.