In the Oslo Diet and Exercise Study (ODES) 219 healthy middle-aged physically inactive persons with moderately deranged risk factor levels (increased bodyweight, diastolic blood pressure, serum cholesterol, triglycerides, decreased HDL-cholesterol) were randomized to 4 intervention groups: dietary intervention, exercise, diet + exercise and control. The purpose of the study was to test if these interventions maintained for a year, isolated or in combination, would change coronary risk factor levels as compared to control. One of the risk factors included was lipoprotein (a) (Lp(a)). The hypothesis to be tested was if physical exercise would be associated with increased levels of Lp(a) as a result of intervention. Those who exercised increased their Lp(a) levels with 15.4 (S.E. = 8.0) mg/l as compared to no exercise (P < 0.05). Also, dietary intervention tended to increase Lp(a), but the increase did not reach statistical significance. There was no detectable interaction on the effect on Lp(a) of the two intervention modalities. A dose-response relationship was found between change in the exercise-specific variables heart rate and peak oxygen uptake, and Lp(a)-change and this dose-response was most pronounced in the exercise group. Change in Lp(a) was associated to change in several lifestyle related variables such as alcohol intake and waist circumference, pointing to the possibility that Lp(a), at least in some subpopulations, is more amenable to change through lifestyle alterations than reported so far.