Many patients receiving cancer chemotherapy become nauseated as they anticipate their treatments. We studied this phenomenon in eighteen cancer chemotherapy patients. The eight patients who reported pretreatment nausea had more extensive disease than the other patients and had received twice as much chemotherapy. In most cases pretreatment nausea developed only a after a number of months of treatment. Nausea was usually precipitated by the odor of the clinic and similar odors elsewhere also caused nausea. Patients continued to experience nausea during follow-up visits after treatment was completed. This syndrome of pretreatment nausea can be understood as a classically conditioned response. Clinical recommendations can be made on this basis.