Kidney biopsies were undertaken for persisting proteinuria 3.3 to 7 years (mean 5.4 years) from the onset of diarrhea-associated hemolytic uremic syndrome (D + HUS) in 5 boys and 2 girls (age at presentation mean 3.2 years, range 1.0 to 9.7 years). At 1 year the mean early morning urine protein/creatinine ratio was 100 mg/mmol, and the mean glomerular filtration rate was 65 mL/min/1.73 m2. At 5 years the mean early morning urine protein/creatinine ratio was 81 mg/mmol, and the mean glomerular filtration rate was 73 mL/min/1.73 m2. The biopsy specimens were compared with those of 7 age- and sex-matched children who were investigated for isolated persistent microscopic hematuria but in whom no abnormality was detected. Global glomerulosclerosis was noted in 6 patients with D + HUS, and 2 of these had segmental sclerosing lesions. Tubular atrophy and interstitial scarring were seen in all but 1 patients. The glomeruli in the D + HUS group were significantly larger than in the control group (P < .01). These findings are typically found in kidneys with reduced nephron numbers and are compatible with changes of hyperperfusion and hyperfiltration in surviving nephrons. Long-term follow-up of patients with D + HUS and proteinuria is advisable.