Sixty-six subjects, 64 of whom were female hospital or medical school employees, were asked if they were willing to take two tablets of "acetylhydroxybenzoate" or a placebo when they next had a headache, after receiving varyingly detailed descriptions of the actions and hazards of the drug. Comprehension and consent to volunteer were inversely related to length of form. In the groups receiving the longer form two subjects volunteered to take the drug despite the presence of contraindications; five subjects missed the point that fatal reactions might occur. When told that the drug described was in fact aspirin, 20 of 21 who had refused to take "acetylhydroxybenzoate" said that they would continue to take aspirin. The data suggest that the information provided to subjects should be brief and to the point, to maximize comprehension and intelligent decision-making. These results have important implications for consent procedures, drug advertising, and drug warnings.