During the past 20 years there has been an increasing number of reports concerning treatment of the family rather than treatment of the individual exclusively. The importance of treating the marital partner as well as the patient is emphasized in the present study by the relatively frequent pathologic reactions of marital partners to patients's improvement or recovery. Just as a patients' failure to respond to treatment may give rise to anxiety, guilt or hostility in his marital partner, so may his improvement lead to similar pathologic reactions. Treatment of the marital partner as well as the patient is indicated when the former reacts to the patient's obvious progress by resisting his improvement or by development of a clinical illness. In such cases the wellbeing of one partner appears to be directly related to the illness of the other and it is not uncommon to find that the less sick marital partner is the first to seek treatment voluntarily. Such pathologic reactions are often predictable and when so, treatment of the marital partner should be instituted as early as possible. The success or failure of the patient's treatment is dependent upon the therapist's ability to deal effectively with both the conscious and unconscious hostility of the marital partner, his resistence to treatment and recovery of the patient, his dependence upon the existence of the patient's illness and the occurrence of his own pathologic reaction to the patient's improvement. The occurrence of specific pathologic reactions by marital partners to patients' improvement or recovery affords an excellent opportunity for further investigation of the etiology and treatment, as well as the prevention of complementary illnesses in marriage.