In persons with hemiparetic stroke, assessment and promotion of fitness have so far received limited attention, partly because of the lack of appropriate measures applicable to them. Because these mobility-impaired persons are prone to inactivity, disuse and insulin resistance are likely to occur, and can aggravate the already significant health and economic consequences that stroke entails. It is therefore important to assess objectively their fitness to devize effective and efficient fitness promotion programs. Because of physical limitations, however, many persons with stroke cannot perform traditional stress testing using a treadmill or a cycle ergometer, and maximal oxygen consumption, which is regarded as a gold standard, is not a practical measure. In this article, we reviewed the current status of research on fitness in persons with hemiparetic stroke from the perspectives of evaluation, structure analysis of fitness, and longitudinal changes during a rehabilitation program. As a measure of fitness, indices obtainable with a submaximal exercise are proposed, such as anaerobic threshold and heart rate oxygen coefficient. Protocols applicable to persons with hemiparetic stroke with a variety of functional limitations have been developed (basic bedside activities, bridging activity, or single arm ergometry). The structure of their fitness is demonstrated to be described by a fitness model of healthy persons (cardiopulmonary, muscular and metabolic dimensions) if the paresis/activities of daily living dimension is added. Several studies suggest that fitness improves during a conventional stroke rehabilitation program. Studying the changes of the above four dimensions can help develop more effective fitness training programs.