The prognosis of lupus nephritis patients in Thailand has been reported to be poorer than that in Western countries since 1978. After a great evolution in management, we re-evaluate the long-term outcome in patients who were treated and followed up at Siriraj Hospital in Bangkok from 1984 to 1991. Clinical and pathologic records were collected from 569 patients (515 females and 54 men) who were followed up for a mean period of 38.7 +/- 34.6 months. The mean age was 28 +/- 10 years and the median duration of symptoms prior to admission was 7 months. Hypertension was diagnosed in 32.4% of patients and 41.3% had serum creatinine greater than 1.5 mg/dL. Nephrotic-range proteinuria was found in 43.6% of patients and creatinine clearance less than 50 mL/min was found in 58.0%. Of the 314 patients who underwent renal biopsy, the most common histologic finding was diffuse proliferative glomerulonephritis (61.5%). The overall probability of survival was 76.5% at 60 and 90 months after diagnosis. Initial presence of hypertension, renal insufficiency (creatinine clearance < 25 mL/min), and World Health Organization histology class IV and III in the biopsied patients were the three independent factors significantly associated with lower survival probability. Neither gender nor amount of proteinuria was the predictive factor for poor outcome. During the follow-up period, 89 patients died and two patients entered a chronic dialysis program. The two leading causes of death were infection (50.5%) and uremia (28.6%).(ABSTRACT TRUNCATED AT 250 WORDS)