The value and development of the copper and magnesium have been examined in thirty-four patients whose eighteen were affected by malignant lymphomas (9 L.H. and 9 non-H.), fourteen by solid tumors and two by acute leukemias. Our results prove clearly a manifest increase of the copper in the lymphomas' patients, especially in the Hodgkin's disease, and in none patients a decrease. Analogous trend has been found in the 71% of the patients with solid tumors. Scarcely significant are the results obtained in the acute leukemias. Contrary to copper, the values of the magnesium are nothing at all expressive for a diagnostic "dépistage"; a light increase of the metal is observed only in the 55% of the lymphomas non-H., while in the cancers the values are very variable. Our results confirm what other Authors have already referred, i.e. the copper's value is of a large aiding for the determination and the valuation of the diseases' activity in the above related conditions.