The aim of this study was to compare short- (0-4 months) and long-term (0-10 months) effects of high-intensive Exercise on Prescription (EoP) intervention (counseling and supervised exercise) implemented in primary healthcare in a number of Danish counties with a low-intensive intervention (counseling) using maximal oxygen uptake (VO(2max)) as the primary outcome. The study was conducted as a randomized trial in 2005-2006 with a high and a low-intensive group. All the patients referred to the EoP scheme by their GP in the counties of Vejle and Ribe, Denmark, were eligible for the trial. The high-intensive EoP group received 4 months of group-based supervised training and attended five motivational counseling sessions. The low-intensive group only attended four motivational counseling sessions. Three hundred and twenty-seven patients entered the EoP scheme, and 52 (16%) volunteered for the randomized trial. No short- or long-term differences were found between the high and the low-intensive groups for VO(2max) (short-term 95% CI -1.1; 4.4 mL O(2)/(kg min), long-term 95% CI -1.6 to 2.1). The present study did not demonstrate any significant clinical outcome for the high-intensive EoP intervention as opposed to the low-intensive intervention.