To evaluate the screening power of the fecal cytokeratin-19 test (CK-19) and the fecal occult blood test (FOBT), we performed rapid fecal CK-19 and FOBT tests on 515 stool samples from patients with various GI diseases and 814 stool samples from control patients. The rapid fecal CK-19 test (developed by DiNonA Research Institute, Seoul, Korea) is based on gold immunochromatography and has a sensitivity of 1 ng/ml. The positive rate of the FOBT was 2.1% in controls, 14.0% in GI cancer patients, 3.5% in GI inflammation patients, 11.7% in bone marrow transplant (BMT) patients, and 6.0% in childhood diarrhea patients. Except for the GI inflammation patients, the patients' positive rates for FOBT were all higher than the controls (p <0.05). The positive rate of the fecal CK-19 test was 8.2% in controls, 42.1% in GI cancer patients, 66.0% in GI inflammation patients, 84.8% in BMT patients, and 19.9% in childhood diarrhea patients. In all of the patient groups, positive rates for the CK-19 test were higher than in the controls (p <0.05). The fecal CK-19 test was more frequently positive (42.1%) in GI cancer patients than the FOBT; if both tests were used, the sensitivity was 49.1%. The fecal CK-19 test (but not the FOBT) gave a higher positive rate in GI inflammation patients than the controls, suggesting that the CK-19 test could serve as a screening test for GI inflammation. The highest positive rate of the fecal CK-19 test was found in the BMT group, indicating that significant GI epithelial desquamation had occurred. Although the positive rate of the fecal CK-19 test in childhood diarrhea patients was higher than in the controls, it was much lower than in adults with GI inflammatory disease. Evidently, children with GI inflammation do not desquamate as much intestinal epithelium as adult patients with GI inflammation. This study shows that the rapid fecal GK-19 test, used in conjunction with the FOBT, may be a valuable screening technique for GI diseases and can assist physicians in the differential diagnosis of GI diseases.