Guaiac tests for faecal occult blood are used for colorectal neoplasia screening. Specificity may be improved by using an immunochemical test for human blood. We evaluated and compared, within an endoscopic study, an immunochemical test for human stool albumin, BM-Test Colon Albumin™, with the guaiac test, Hemoccult® SENSA™. Both tests were given to 527 screenees who had had a low-peroxidase diet before and during the tests. All had a colonoscopic (59%) or flexible sigmoidoscopic (41%) examination. Both tests were easy to perform and develop. They were of similar sensitivity (35–30%) for adenomas ≥ 1.0 cm in diameter or cancers, but Colon Albumin™ had a higher specificity (90%) than Hemoccult® (85%P< 0.05). The latter, however, had a higher sensitivity for neoplasia of all sizes (25%vs20% NS) but lower specificity (85%vs90%P< 0.05). Colon Albumin™ was positive in 11.2%, while Hemoccult® SENSA™ was positive in 16.7% and appears very sensitive to dietary peroxidases. Positivity was reduced to 7% by changing the methodology protocol. Overall, the guaiac test is more sensitive but less specific than the immunochemical test for colorectal neoplasia. However, the technical and diagnostic limitations of these tests must be appreciated, and because of their high positivity rate neither is suitable for mass screening. A more specific test for neoplasia is needed.