Crohn's disease (CD), a chronic relapsing inflammatory condition of the intestines, is a common cause of gastrointestinal morbidity in young people. Although the aetiology of CD is unknown, host, genetic and environmental influences are clearly important. Glucocorticoids remain the mainstay of treatment for active CD, however only two-third of patients will respond and side effects are considerable. Surgery is often undesirable or impracticable and therefore alternative medical strategies have been sought. In recent years, there has been much interest in two areas of IBD therapy-the use of established immunomodulators, and the development of novel biological therapies. In this review, we have selected two areas of particular controversy-the use of purine analogues (azathioprine (AZA) and 6-mercaptopurine (6-MP)) and the introduction of anti-tumour necrosis factor alpha (TNFalpha) therapy and have examined the data for efficacy, safety and tolerability of these medications.