At present there are about 1 million trained cardiopulmonary resuscitation (CPR) rescuers in Sweden. CPR out-of-hospital is initiated about 2000 times a year in Sweden. However, very little is known about the bystanders' experiences and reactions. The aim of this study was to describe bystander-initiated CPR, the circumstances, the bystander and his experiences. All CPR bystanders in Sweden who reported their resuscitation attempts between 1990 and 1994 were approached with a phone interview and a postal questionnaire, resulting in 742 questionnaires. Bystander-initiated CPR most frequently took place in public places such as the street. The rescuer most frequently had problems with mouth-to-mouth ventilation (20%) and vomiting (18%). More than half (53%) of the rescuers experienced CPR without problems. Ninety-two percent of the bystanders had no hesitation because of fear of contracting the acquired immunodeficiency syndrome (AIDS) virus. Ninety-three percent of the rescuers regarded their intervention as a mainly positive experience. Of 425 interviewed rescuers, 99.5% were prepared to start CPR again.