[en] In 60 women with breast cancer the effect of radical mastectomy and radiotherapy on the serum levels of immunoglobulins IgA, IgM and IgC was studied. It was demonstrated that surgical treatment had no significant effect on the levels of immunoglobulins in the serum. Following X-ray therapy a fall occurred in the level of immunoglobulins, mainly of the IgA class, less in that of IgM and IgG. Radiation-induced disturbances were greatest immediately after completion of treatment and disappeared only after about 12 months. The degree of disturbances in the level of IgA was increased when the thymus was exposed to radiation, this was less evident in the level of IgG. (author)