Deep water running with wet vest is a safe form of exercise for elderly with mobility limitations. However, it is not known to what extent their aerobic power may be improved. Therefore, the aim was to assess the effects of high intensity deep water interval training with vest in elderly women. Twenty-nine healthy women 69 +/- 4 years old participated. They performed a graded maximal exercise test on the cycle ergometer. They were randomly assigned to a control or to a training group. A submaximal exercise test on the cycle ergometer was executed only by the training group. They trained in deep water running/walking wearing a vest two times a week for 8 weeks. The target heart rate was 75% of maximal heart rate and the training consisted of several short working periods and resting intervals. After the intervention the heart rate at rest was 8% lower for the training group (P<0.01). Their heart rate at submaximal exercise was 3% less (P<0.01), their maximal oxygen uptake was raised by 10% (P<0.01), and their maximal ventilation was increased 14% (P<0.01). The values for the control group were unaltered after the period of intervention. In conclusion, high intensity deep water running with vest improves submaximal work capacity, maximal aerobic power, and maximal ventilation with the effects transferable to land-based activities in elderly women.