BACKGROUND Renal abnormalities are often seen in sickle cell disease (SCD). OBJECTIVE To investigate the role of hydroxycarbamide as a protective agent in sickle cell nephropathy. METHODS Patients with SCD followed at a Hematology outpatients clinic. METHODS Prospective study with 26 SCD patients. Renal function evaluation was performed and a comparison between patients and control group was done. Patients using hydroxycarbamide were compared to those not taking this drug. METHODS Effect of hydroxycarbamide on renal function. RESULTS Patients mean age was 32.1 ± 9.9 years, and 16 (61 %) were males. Glomerular hyperfiltration was found in nine patients with SCD (34.6 %). GFR < 60 mL/min/1.73 m² was observed in three cases (11.5 %). Microalbuminuria (30-300 mg/day) was found in seven cases (27 %) and macroalbuminuria (>300 mg/dia) in one patient (3.8 %). All patients had urinary concentrating deficit, and inability to acidify urine was found in ten cases (38.4 %). The comparison of patients according to the use of hydroxycarbamide showed lower levels of serum creatinine in those using the drug (0.6 ± 0.1 vs. 0.8 ± 0.3 mg/dL, p = 0.03), as well as lower levels of 24 h-proteinuria (226 ± 16 vs. 414 ± 76 mg/dL, p = 0.0001), but not microalbuminuria (79 ± 15 vs. 55 ± 86 mg/dL, p = 0.35). CONCLUSIONS SCD is associated with important renal abnormalities. Hydroxycarbamide seems to protect kidney function in SCD by decreasing proteinuria but not microalbuminuria.