The theoretical knowledge and practical performance of 166 lay people attending a short cardiopulmonary resuscitation course were evaluated according to the American Heart Association standards. Before tt course no participant was able to perform even a bad attempt at cardiopulmonary resuscitation. Theoretical knowledge was good at the end of the course and at the refresher course six months later. At the end of the initial course 65% (57/88) of the participants examined could adequately compress and ventilate the manikin. After six months 44% (30/68) could perform resuscitation adequately. Women were as proficient as men, and elderly people in general were as proficient as the younger ones. The skill of carotid artery palpation was surprisingly well retained after six months. Data on pulmonary ventilation and cardiac massage were recorded simultaneously on a recording resuscitation manikin. When these objective data were compared with the American Heart Association standards only a few participants were able to perform correct cardiopulmonary resuscitation. The number of compressions and ventilations per minute were often insufficient. A large discrepancy between self, subjective, and objective assessment of cardiopulmonary resuscitation knowledge and performance was found. The importance of a rapid diagnosis, an immediate call for help, an adequate rate of cardiac massage, and a reduction in the time needed for ventilation should be emphasised at these courses. Refresher courses should be provided at least twice a year.