Questionnaire data on about 1200 male twin pairs from the Registry at the Karolinska Institute, Stockholm, and on about 4000 male twin pairs from the Registry of the National Research Council, Washington, DC, have been used to study factors affecting angina pectoris. An operational definition of "angina pectoris" was developed from the questionnaire. In the available data, alcohol drinking, lack of exercise, frequent change of employer, low occupational adjustment and smoking are moderately but significantly related to angina among individuals (disregarding twin relationships) in both Sweden and the US. In monozygous US twin pairs discordant for the above variables, significantly different rates of angina appear only with alcohol drinking. In discordant dizygous US twin pairs, significantly different rates of angina appear with alcohol drinking and with low occupational adjustment. Of the independent variables only smoking and drinking are appreciably associated with each other. These findings suggest that alcohol drinking and to a lesser extent occupational adjustment are related to angina directly and not through their association with other factors such as age, genetic background, smoking, physical exercise and early environment.