Clinicians are becoming increasingly interested in the use of aerobic training to enhance functional outcomes after stroke. Several studies have demonstrated the effectiveness of training among individuals in the chronic poststroke period. However, there is limited information on the response to training in earlier stages of recovery. The purpose of this article is to review what is known regarding the capacity of people early after stroke (<4 months) to respond to the physiological demands of exercise (exercise capacity) as well as their ability to make long-term cardiovascular adaptations to aerobic exercise. There is evidence that exercise capacity, as measured by peak oxygen consumption on maximal exercise tests, is reduced in this population. There is also evidence, albeit limited, that exercise trainability soon after stroke can be both feasible and safe, if appropriate screening and monitoring are used. Moreover, there are early indications that activity-level functions such as walking speed, mobility, and balance may be enhanced through such programs. Further research is necessary to elucidate the most appropriate timing and design of fitness programs for people early after stroke.