The management of inflammatory bowel disease depends on knowledge of the site, extent and severity of inflammation. Early work showed that 111In-labelled white cells could fulfil this role. More recently. 99mTc-HMPAO white cell scanning was introduced. Several studies have shown that this test can reliably detect disease and can assess extent. Simple visual grading of uptake intensity can also be used to assess severity. The improved image resolution allows assessment of small bowel disease in addition with high sensitivity in the detection of ulcerating Crohn's disease. Other causes of bowel inflammation should be excluded. Complicating abscesses can be detected and the inflammatory component of strictures can be assessed. False positive activity can be avoided by imaging early at one hour, before such non-specific excretion occurs. Later images are also useful in order to help localize disease, but only in addition to the initial one hour scan. 99mTc-HMPAO white cell scanning, a simple non-invasive, highly informative test should be added to the armamentarium of every gastroenterologist.