In the present thesis a model is developed to calculate characteristic marks for classification of malign human tissues in the digestive tract. Different physiological and toxic elements were quantitatively determined in 68 malign tissue samples and in their corresponding healthy tissue samples from stomach, colon, and rectum by total-reflection x-ray fluorescence analysis. Microtom and high pressure digestion were used as preperation methods for the determination. A matrix was built using the element distribution, personal and pathological data to use it for t-test, principal component analysis, linear dicriminant analysis and regression. Significant higher values of phosphorus, sulphur, potassium, selenium und rubidium could be detected in the malign tissues. The calculation of grading and pT-class in comparison with the determined values results in correlation factors between 0.76 and 0.92.