Most attrition research has focused on dropping out once the patient has arrived at the clinic. However, many potential patients, who are in need of service, do not contact clinics. Such patients are said to be in the appraisal stage of treatment. Discontinuation of appraisal, for whatever reason, can be termed "attrition." Such attrition has not received adequate attention. A conceptual model of the appraisal process is given, and a review is made of current research bearing on the conditions under which appraisals continued or discontinued by an individual. Recommendations for future research are made.