The effects of physical restraint and poly I:C treatment on the growth of MOPC 104E myeloma and murine osteosarcoma and survival of animals bearing such tumors were investigated. Our studies show that in the Balb/c mice with MOPC 104E myeloma the effects of restraint stress were detrimental and lead to early death of the mice. When the restraint was combined with poly I:C, during the early course of the disease, restraint stress neutralized the beneficial effects of the poly I:C treatment. These studies show that under certain circumstances, restraint stress can negate the effects of therapy. On the other hand, restraint stress produced an opposite effect in C3H/He mice with murine osteosarcoma tumor treated in the same fashion. In mice with osteosarcoma, restraint stress delayed tumor growth and increased the median survival time. When restraint stress was combined with poly I:C treatment, the mean tumor size was smaller and median survival was substantially increased over the control group. Because poly I:C therapy delayed tumor growth and increased survival in both models, efforts to strengthen this response were tested by conditioning. Our studies show the response to poly I:C as measured by elevation of the NK activity could be conditioned with camphor smell. Conditioning of the host to raise immune activity to alter the outcome of disease is a new area yet to be explored and has important clinical significance. These studies, we believe, are important because they explore the connection between mind and body and resistance to disease.