All psychiatrists in the greater Cincinnati area were sent a series of three questionnaires concerning patients from nonstructured discussion or T-groups. Twenty-four respondents reported having seen patients who had become psychotic or acutely disorganized in association with such group activity. They received a fourth questionnaire asking for details about the 19 patients involved and about the groups in which they participated. These 19 cases came from an estimated population of sensitivity-group participants of 2,900(0.66% casualties). Few (only five out of 1,750, or 0.28%) had been in structured "managerial grid" groups. Both positive and negative aspects of participation in sensitivity groups were elicited from the reported experience of these psychiatrists.