A preliminary study was conducted to compare the BrK alpha/RbK alpha peak intensity ratio in colorectal cancer (CRC) patients and healthy subjects (controls) in Israel. Blood samples were obtained from 61 CRC patients and 124 controls. The controls represent a normal population from different areas in Israel. Three hundred microliters of wet whole blood samples were analyzed by the EDXRF method. A weighted mean of 2.45 +/- 0.38 Br/Rb ratio was obtained for CRC patients, as compared with 3.28 +/- 0.40 Br/Rb ratio for controls. The mean value for controls represents only 112 subjects, since 12 individuals of the control group suffered from some other diseases and therefore were not included for the mean value calculation in this group. The results indicate that the Br/Rb ratio in CRC patients is significantly lower (p < 0.05) than in controls. No significant difference was found in Br/Rb ratio correlated to age and sex. It was not possible to draw final conclusion concerning the relationship between the Br/Rb ratio and the malignancy stage, since there was a relatively small number of cases in each stage under investigation.