Subjective fatigue, defined as a feeling of early exhaustion developing during mental activity, with weariness, lack of energy and aversion to effort, remains virtually unstudied in patients with stroke, bur recent surveys suggest that it is a major, commonly overlooked, stroke sequela. While the few existing series did not show significant correlations between fatigue and stroke severity, lesion location, cognitive and neurological impairment and depression, recent neurobehavioral studies have highlighted an association between fatigue and brainstem and thalamic lesions. This suggests that fatigue may be linked to the interruption of neural networks involved in tonic attention, such as the reticular activating system. In fact, several subtypes of fatigue may develop after stroke, in connection with cognitive sequelae, neurological impairment, psychological factors and sleep disorders. A challenge is to identify and delineate these different subtypes and to distinguish them from mood disorders, which frequently coexist. We emphasize the concept of 'primary' poststroke fatigue, which may develop in the absence of depression or a significant cognitive sequela, and which may be linked to attentional deficits resulting from specific damage to the reticular formation and related structures involved in the subcortical attentional network. In the patients with excellent neurological and neuropsychological recovery, poststroke fatigue may be the only persisting sequela, which may severely limit their return to previous activities. The recognition of poststroke fatigue may be critical during recovery and rehabilitation after stroke.