This paper focuses on the effect of cancer on the patient's interpersonal relationships, and the ultimate impact of these relationships on the patient's emotional adjustment to the disease. In a detailed theoretical analysis, both the patient's reaction to the illness and others' responses toward the patient are explored. Concerning the patient, the following issues are discussed: (1) fears and uncertainties that develop as one attempts to cope with the diagnosis; (2) the consequent need for clarification and support; and (3) the barriers to receiving validation and support from others. Others' reactions to the patient are hypothesized to be a function of a conflict between (1) their feelings about the illness, which are predominantly negative; and (2) their beliefs about appropriate behaviors to display when interacting with cancer patients (optimism and cheerfulness). This conflict results in behavioral responses that are unintentionally damaging to the patient, including physical avoidance, avoidance of open discussion of the illness, and discrepancies among behaviors. The impact of others' behavior on the patient and the patient's subsequent attempts to solve their interpersonal problems are discussed. The paper concludes with implications for intervention and research.