The aim of the present study was to identify factors that account for similarities and discrepancies in classification of Type A and B behavior by the Structured Interview (SI) and by the Jenkins Activity Survey (JAS). Two diverse samples were administered the SI and the JAS. SI questions were coded for content of response and psychomotor behavior during the interview. Frequency of specific Type A speech characteristics and clinical judgments were also rated. Analyses revealed that the SI estimate of Type A could be predicted by the subjects' promptness of response, voice emphasis, hurried speech, and judgements of competitiveness, hostility, and energy level. The latter three judgments were also measured somewhat by the JAS. Interviewer ratings of subjects' overt motor behavior and appearance did not relate to SI assessments. The JAS estimate of Type A could be predicted by subjects' reports of pressured drive, which was also measured by SI. This pattern of interrelationships was similar in the two samples in spite of sample differences in age, health status, geographical location, interview and JAS forms, and raters. Overall, the correlations between the SI and JAS assessment were low and suggested a considerable degree of independence between the two measures. In light of these results, they should not be used as interchangeable measures of Type A behavior.