This study investigated and compared the effectiveness of T groups and the Human Development Institute (HDI) in changing interpersonal perception styles and communication skills. In 20 hours of instruction over a ten week period, the two training conditions were systematically varied with groups of elementary school teachers differing on the personality variable of conceptual level (CL). Thirty trainees were divided into four experimental groups: low CL HDI; low CL T group; high CL HDI; and high CL T group. Nine elementary teacher trainees were used as controls. All subjects were pretested and posttested on the two variables. T group and HDI training both proved effective, for the different CL groups, in improving communication skills; neither was effective, for any treatment group, in affecting interpersonal style. Controls showed no significant change on either variable. As regards communication skills, the HDI procedures were slightly more effective with low CL trainees, while T groups were slightly more so with high CL trainees. Conclusions and generalizations must be qualified by such limiting factors as the small sample, a highly selective experimental group, and the absence of an adequately matched control group. (author/ly)