Results of four studies in which the semantic differential was used to evaluate teaching effectiveness of professors at the university level are presented. Conclusions based on comparisons between factors isolated in the four studies, as well as between these four studies and other data, are as follows: (1) some factors such as teaching dynamism, acceptance-change and action freedom appear over time and with different populations; (2) the proportion of variance accounted for by each of these factors varies between populations studied and from one factor analysis to another; and (3) the semantic differential seems to be an especially useful technique for quantifying emergent variables associated with student perceptions of teaching effectiveness and effective professors. Tables present the study data. (DB)