Objectives. It has previously been shown that patients with active JDM have decreased aerobic fitness; however, it is not known whether these patients regain their physical fitness after recovery. The objective of this study was to investigate the long-term outcome of aerobic fitness in patients with JDM. We hypothesized that fitness (VO(2max)) is reduced compared with healthy controls in the years after active JDM. Methods. A maximal exercise test was performed using a cycle ergometer. Results were compared with those of sex- and age-matched healthy controls. Results. A total of 36 patients with JDM in remission were included, 2-36 years after disease onset. Twelve patients (33%) had normal VO(2max) and 24 patients (67%) had decreased VO(2max). Mean VO(2max) was higher in the healthy controls vs patients (P <0.001, 95% CI -10.7, -4.4). A significant difference between patients with JDM and controls was observed for women (P <0.001), men (P = 0.04), children <18 years (P = 0.002) and adults > 18 years (P = 0.01). The decreased VO(2max) was independent of the duration of remission, but it was associated with the duration of active disease. By linear regression, it was revealed that for every year of active disease, VO(2max) was reduced by 0.85 ml/min/kg on average (P <0.001). Conclusion. This long-term follow-up study demonstrates that patients who have had JDM have persistently impaired fitness. This impairment is directly related to the duration of active disease.