From the standpoint of utilizing a distinctive feature of para-aminobenzoic acid (PABA) and intestinal bile acid metabolism, a conjugate of ursodeoxycholic acid with PABA (PABA-UDCA) was newly synthesized for studying whether it can be a good material or not to evaluate enteric bacteria. In incubation experiment, this compound was reasonably deconjugated by cholylglycine hydrolase resulting in the release of PABA. In animal experiment, urinary excretions of PABA were determined during six hours following oral administration of 10 mg PABA-UDCA. Control rats (n=7) excreted 140.1 ± 59.5 μ,g (mean ± SD) of PABA. By contrast, the rats (n=9) with intestinal antisepsis by antibiotic administration excreted less (18.3 ± 16. 7 μg; P < 0.001) whereas those with intestinal bacterial overgrowth by making enteric blind loop excreted more (451.1 ± 223.6 μg; P < 0.01). These observations indicate that this new compound is likely to offer a simple and rapid method for evaluation of the intestinal microorganisms.