The compounds resulting from the reaction of glucose with proteins (advanced glycation products) can be important markers of chronic diabetic complications. To test the possible diagnostic value of advanced glycation products containing the furoyl moiety, collagen samples from diabetic and healthy rats were analyzed by parent ion spectroscopy. In our study, we compared normal collagen, diabetic collagen and normal collagen incubated with different glucose concentrations and we employed different hydrolysis procedures (HCl and proteinase). Mass spectroscopic measurements performed on hydrolyzed samples showed that either different samples or different hydrolysis procedures produce a similar set of furoyl-containing compounds. 2-(2-Furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI) which has been reported to be one of the advanced glycation products, was never found in any of the samples examined. Hence neither FFI nor furoyl-containing molecules can be considered markers of advanced glycation processes.