Quantitative changes of some selected serum proteins in rats irradiated with a single dose of 2 Gy neutrons were compared with protein changes in rats irradiated with an equal single neutron dose and subsequent continuous gamma irradiation using daily dose rate of 0.574 Gy up to the total dose of 6 Gy. On the basis of the values obtained from the diagrams of two-dimensional immunoelectrophoresis it was found that both irradiations entailed approximately equal quantitative changes of the serum concentrations of the proteins followed. The differences found concerned time intervals of the adjustment of the changes produced. After neutron irradiation reparation of the serum albumin occurred on 14th day, of A1-globulin concentrations on 28th day and of haptoglobin on 90th day, yet after combined neutron and gamma irradiation reparation of the changes in albumin on 15th and A1-globulin occurred on 40th day and in haptoglobin only on 100th day after neutron irradiation.