We previously reported a phase I study of intravenous irinotecan plus oral ciclosporin, in which dose-limiting diarrhoea was not observed, supporting the hypothesis that pharmacokinetic modulation of irinotecan by ciclosporin may improve its therapeutic index. We now report results of a further 34 patients treated at the recommended dose. A low rate of diarrhoea of grade 3 or above (3%) was again seen, with useful anti-tumour activity. The regimen is to be formally evaluated as part of a future phase III trial.