Six patients with an evident multiple sclerosis (MS) were observed in dynamics of long term immune therapy based on administration of rIFN preparations. One half of them received the therapy with rIFN-alpha. Three other patients received rIFN-beta administration that was interrupted, when sensitivity of blood cells to in vitro IFN-beta action was decreased; the trial was continued by rIFN-alpha courses. Production of IFN-alpha and IFN-gamma by stimulated peripheral blood leukocytes (PBL) of the patients was tested simultaneously with detection of in vitro PBL response to IFN-alpha, IFN-beta and IFN-gamma priming action every 10th day of observation. It has been shown that positive clinical effect of rIFN-alpha therapy following rIFN-beta administration was comparable or even surpassed neurological effects of rIFN-alpha and rIFN-beta applied alone. Similarly rIFN-alpha and rIFN-beta therapy caused a partial restoration of initially decreased IFN-alpha and IFN-gamma production by PBL. It has been also accompanied by the dissociation appearance between IFN-alpha and IFN-gamma production by PBL, when in accordance with physiological IFN system state restoration the IFN-alpha production was augmented while IFN-gamma synthesis was reduced. Such a dissociation was paralleled by decrease in PBL response to IFN-alpha treatment, by increase in blood cell sensitivity to IFN-beta action, and by keeping IFN-gamma response at lower level than during rIFN-alpha or rIFN-beta caused dissociation. The data obtained allowed to confirm the possibility to combine rIFN-beta pathogenetical therapy with rIFN-alpha administration in patients with MS when sensitivity of blood cells to IFN-beta action displayed a tendency to a fall.