The diagnostic values in detecting terminal ileum dysfunction using [75Se]HCAT have been assessed for two different scintigraphic techniques in 58 subjects. The measurement of [75Se]HCAT T1/2 in the enterohepatic circulation by daily gallbladder scintigraphy showed 78% sensitivity, 96% specificity, 96% positive predictive value, and 78% negative predictive value at the optimal cutoff level of 2.0 days; lower--but not significantly different--figures were observed for [75Se]HCAT total abdominal retention four and seven days after isotope administration, at the optimal cutoff levels of 40% and 22%, respectively. [75Se]HCAT T1/2 was then evaluated in 60 patients with various intestinal diseases. Sixty-nine percent (9/13) of patients with diarrhea of obscure origin showed abnormal [75Se]HCAT T1/2. Bile acid malabsorption using [75Se]HCAT can be investigated by the noninvasive measurement of its enterohepatic T1/2 and may play a pathogenetic role in patients with diarrhea of obscure origin.