Abdominal aortic aneurysm (AAA) is a ballooning-out of the aorta that does not normally give any symptoms. Undetected and untreated an aortic aneurysm can rupture, which in most cases is fatal. Mass screening of 65-year old men for the early detection of AAA and, in selected cases, operation seem to reduce mortality due to rupture, although, screening has not reduced the overall mortality in this group. In Västra Götaland, the southwest part of Sweden, screening for AAA amongst 65-year old men started in 2009. There are controversies within the medical community about the benefits and adverse effects of screening. In order to explore men's experiences of being screened and knowing they had an aortic aneurysm, we undertook a qualitative interview study with 15 men who in the screening programme were identified as having an aortic aneurysm and who were to be followed-up with annual ultrasonic examinations for an indeterminate number of years. The interviews were analysed for categories and themes using content analysis. The study found that the men were ambivalent about the knowledge that they had an AAA and about the follow-up monitoring. They appreciated having the knowledge but it was accompanied by worry, feelings of anxiety and existential thoughts about the fragility and finiteness of life. We recommend that before a screening programme is implemented, the psycho-social consequences should be thoroughly investigated. Participants should be given adequate and understandable information about the consequences of screening so that they can make an informed choice whether to participate or not.