Twenty-three patients with an acute event of coronary heart disease (CHD) received routine care including information about medication and lifestyle changes. They were interviewed after 1 year about their conceptions concerning drug treatment and lifestyle changes. The interviews were taped, transcribed and analysed using the phenomenographic approach. Conceptions were hierarchically categorised with regard to level of understanding. The results showed that the patients' understanding of the effects and health benefits of their treatment was superficial as judged on an informed layman level. The knowledge was fragmentary and mechanistic. Several misconceptions were revealed. Few answers related to prognostic benefits. However, a conception about effects of stopping drug intake was risk of relapse. Some patients considered fate and heredity as the main causes of CHD. Thus, our patients had not achieved an adequate understanding of CHD treatment. The level of knowledge was lower than anticipated.