Abnormal illness behavior (AIB) has been proposed as a construct measuring the inappropriate or maladaptive modes of responding to one's state of health, and the Illness Behavior Questionnaire (BQ; Pilowsky, 1975) was designed to measure this construct. Previous studies using small samples have failed to agree on the factor structure of this questionnaire. The present paper examines the factor structure of the Illness Behavior Questionnaire and critically evaluates the interpretation of its dimensions as well as the construct of AIB. A factor analysis of responses from 1,061 health care and nonhealth care seeking subjects yielded six interpretable factors which substantially replicated Pilowsky's previous results. Six scales were calculated and correlated with several personality measures. The results indicated that the Illness Behavior Questionnaire is saturated with neuroticism, a dimension known to be related to excessive medical complaints. But excessive medical complaints cannot be equated with hypochondriasis or AIB in the absence of objective medical information. In the absence of evidence for the discriminant validity of the IBQ, its use as a diagnostic device is unwarranted. Treating elevated IBQ scores as indicators of abnormal illness behavior without corroborating medical information may be more misleading than accepting patients' symptom reports at face value.