Renal involvement is a rare occurrence in juvenile rheumatoid arthritis (JRA). We report on two JRA patients with kidney disease. The first was a 14-year-old African-American female with a 12-month history of polyarthritis. On presentation she was found to have an ESR of 127 mm/h and a positive ANA, rheumatoid factor (RF), perinuclear antineutrophil cytoplasmic antibodies (pANCA), haematuria, proteinuria with normal BUN and creatinine. Renal biopsy showed focal segmental glomerulosclerosis. Her renal function deteriorated to end-stage renal failure requiring dialysis within a few months, despite aggressive treatment with steorids and monthly i.v. pulses of cyclophosphamide. The second patient presented with a 6-week history of polyarthritis and intermittent fever, and had a salmon-coloured evanescent rash. On presentation his laboratory evaluation was significant for elevated ESR and negative ANA, RF and ANCA tests. Within 8 months the patient had developed a persistent microscopic haematuria. Renal biopsy showed mild mesangial glomerulonephritis. On low-dose methotrexate therapy his JRA went into remission and his renal function remained normal. The haematuria persisted for 1 year and then resolved spontaneously. This is the first time that focal segmental glomerulosclerosis and mesangial glomerulonephritis have been described in JRA. Although the association may be just coincidental, further studies are needed to define the role of JRA in these renal conditions. In patients with JRA, urinalysis and renal function should be routinely monitored.