1.   Sensitive indicators of renal function in a group of patients maintained on long term, delayed release mesalazine and a comparable group on sulphasalazine have been studied.

2.   In this study, long term maintenance treatment with delayed release mesalazine was no more nephrotoxic than continued treatment with sulphasalazine.

3.   We have therefore studied sensitive indicators of renal function in a group of patients maintained on long term, delayed release mesalazine and a comparable group maintained on sulphasalazine.

4.   Recently, a number of cases of nephrotoxicity have been reported in patients taking delayed release mesalazine.

5.   In this study we have assessed renal function in a group of patients who have been maintained on delayed release mesalazine from six months to over six years.