Sarcoidosis is a chronic relapsing multi-systemic disorder characterized by the development of non-caseating granulomas. Granulomatous tubulo-interstitial nephritis is an uncommon manifestation of this condition. We identified 39 patients with sarcoidosis and renal disease from a single center of whom 17 patients had biopsy-proven tubulo-interstitial nephritis. They were analyzed with respect to demographic and clinical features, including response to corticosteroids and length of follow-up. They all presented with significant renal impairment. At presentation the mean+/-s.d. estimated glomerular filtration rate (eGFR) was 26.8+/-14 ml/min by modification of diet in renal disease (MDRD) equation 7. With treatment there was a significant improvement in renal function with eGFR 49.6+/-5.2 ml/min (P<0.01) at 1 year, and 47.9+/-6.8 ml/min (P<0.05) at the last review. The median follow-up was 84 months (range 6-284 months). Patients with chronic kidney disease (CKD) 3, the mean eGFR was 38.30+/-2.4 ml/min at presentation and 60.2+/-7.4 ml/min at 1 year (P=0.02) and in CKD 4 it improved from 19+/-2 to 38+/-6.6 ml/min at 1 year (P<0.05). After the 1st year, the change in eGFR was +0.8 ml/min/year for CKD 3 and -2 ml/min/year for CKD 4 (P<0.05). Three patients ceased their therapy either due to complications or poor compliance and experienced a worsening of renal function which was then reversed on re-commencing corticosteroids. Corticosteroids are effective in advanced tubulo-interstitial nephritis due to sarcoidosis. Long-term treatment is necessary to preserve renal function and to delay the onset of end-stage renal disease.