In order to determine the pattern of renal disease and risk factors for renal disease in HIV-infected Nigerians, we studied 400 consecutive HIV/AIDS patients (210 males, 190 females) aged between 18 and 65 years (mean +/- SD; 34.6 +/- 9.4 years), and examined renal disease factors attributable to the infection. Diagnosis of renal disease was based on the consistent presence of at least 1+ albuminuria and/or elevated serum creatinine (>132 micromol/l) as well as the absence of other identifiable causes of chronic kidney disease (CKD). We determined socio-demography and clinical findings, as well as full laboratory work-ups including haemogram, CD4+ cell count, serum electrolytes, urea, creatinine, protein, cholesterol and urine analysis. Renal biopsies were taken in 10 patients who had moderate to massive proteinuria and had consented to the procedure. Finally, we compared HIV/AIDS cases with and without renal disease to determine the risk factors for nephropathy. We observed a high prevalence of renal disease (proteinuria and/or elevated serum creatinine), which was present in 152 (38%) of the patients. This subgroup included 74 males and 78 females with a M:F ratio of 1:1. The mean age (+/-SD) was 35.8 (+/-10.01) years. Systolic and/or diastolic hypertension was seen in 13.2% of these patients while the mean (+/- SD) body mass index (BMI) and packed cell volume (PCV) were 18.5 (+/-3.1) kg/m(2) and 25.26 (+/-6.81)%, respectively. The mean (+/-SD) CD4+ count was 246.49 (+/-192.8) cells/microl, while the mean (+/-SD) serum creatinine and 24-h urine protein excretion rates were 210.11 (+/-337.8) micromol/l and 2.57 (+/- 2.42) g/day, respectively. In subjects with and without nephropathy, there were significant differences in age, BMI, serum cholesterol, serum albumin and CD4+ counts, suggesting that these parameters may be risk factors for nephropathy. Histology revealed mainly focal glomerulosclerosis (FGS) with glomerular collapse. We conclude that the prevalence of proteinuria in HIV-seropositive patients is high in Nigeria. Such subjects show an equal male:female distribution, and glomerular histology revealed that a majority of biopsied patients had the collapsing FSGS variant. The risk factors for renal disease included severity of the HIV infection (inferred from the generally low CD4+ count), anaemia, malnutrition and increasing age.