A considerable body of evidence is presented showing a substantial degree of longitudinal as well as cross-situational consistency in the motive area of aggression. These data demonstrate that the influential conclusions with regard to consistency drawn by Mischel in his evaluative review (1968, 1969) are not supported by existing empirical evidence in the field of aggression. The consistency found makes it both defensible and natural to assume the 'existence' of some kind of relatively stable, individual-differentiating aggressive reaction tendencies within the individuals, however conceptualized. Furthermore, on the basis of a conceptual analysis, it is shown why low correlations have often been found between self-report data (S data) and rating data (R data), on one hand, and objectively recorded behaviour (T data), on the other. It is argued that the reasons are often to be found in a conceptual mismatch as well as in psychometric insufficiences of T data. This analysis has broad implications for personality measurement in laboratory settings in general.