Abstract: The invention is used for the diagnosis of human tumoral diseases. The diagnosis method consists of preparing films from patient arterial and venous blood, processing said films using a conventional method such as fixing or dyeing, measuring the surface areas of the arterial and venous blood lymphocyte nuclei and comparing said surface areas to corresponding cell surface areas of different lymphocyte groups, plotting regression lines for the arterial and venous blood according to the values thus obtained, determining the percentage thereof for each lymphocyte group, plotting the influence curve thereof in the form of a function of the diameter of corresponding lymphocyte groups, introducing weight factors whose quantity increases along the lymphocyte diameter decrease, multiplying said factors by the lymphocyte percentage, and plotting the sums' correspondence for the arterial and venous blood in the form of the function of the difference therebetween.