The data presented in this paper examine the frequent statements that the regular use of the drug qat by the people of North Yemen is harmful to their health. The research strategy employed performance of blind physical examinations as well as extensive interviews with 335 females and 371 males in and around the cities of Sanaa, Taiz and Hodeida who had been selected using a quota sample. The sample was classified into heavy, light and non-chewers of the qat plant, and systematic comparisons were made. In general, few diseases or conditions occurred with enough frequency to permit detailed analysis and fewer yet were associated with qat-use. Where associations occurred, differences by sex were often strong. Conditions most strongly associated with use by both sexes were histories of gastritis and insomnia, and the general body system groupings of gastrointestinal disorders. In males the strongest associations were with the histories of anorexia, constipation, insomnia and headaches, as well as the general history of respiratory difficulties. In females strong associations were seen between qat-use and the diagnosis of acute gastritis, and histories of jaundice, bronchitis and hepatic diseases. When effects of age and residence were corrected for by Mantel-Haenszel odds ratios on these items, some of the associations were diminished even further. In general, remarkably few of the allegations regarding the direct effects of qat-use on health by Western visitors to Yemen were supported by this study.