5-Aminosalicylic acid (5-ASA) is the most commonly used drug for the treatment of inflammatory bowel disease (IBO). 5-aminosalicylic acid induced nephrotoxicity has recently been reported. We report a case of female with Crohn's disease treated with mesalazine for 60 months and sulphasalazine for additional 12 months. The patient presented with loin pain, sterile pyuria and raised serum creatinine. Percutaneous renal biopsy revealed chronic interstitial nephritis and yellow-brown pigment deposition in proximal tubular cells. Steroid treatment was commenced for 4 months and there has been no improvement in renal function. Due to widespread use of mesalazine, and its insidious onset of nephrotoxicity, renal function screening and urinalysis should be routinely performed to detect the toxicity of mesalazine and related drugs.