The syndrome of the supplementary motor area (SMA) is not well recognized and its features can easily be confused with pyramidal weakness. The authors describe the SMA syndrome in six patients who underwent surgery for tumours located in the SMA, three in the dominant and three in the non-dominant hemispheres. All of them underwent complete resection of the anatomically described SMA, with partial (n = 4) or total resection (n = 2) of the tumour. In the postoperative period, all these patients exhibited reduction of spontaneous movements and difficulty in performing voluntary motor acts to command in the contralateral limbs, although the tone in the limbs was maintained or increased. The function of these limbs in serial automatic motor activities (for example, dressing and walking) was, however, relatively unaffected. Speech deficits were seen in only one of three patients with the dominant SMA syndrome. Besides a severe impairment of volitional movements, the salient features of the deficits in this syndrome are hemineglect and dyspraxia or apraxia involving the contralateral limbs. All patients recovered their motor functions over varying periods of time ranging from one to a few weeks. Long-term follow-up (median 24 months) in five patients revealed complete return of function in the affected limbs. It is important to recognize the entity of the SMA syndrome and differentiate it from the deficits that result from operative damage to the motor cortex as the deficits associated with the former are likely to recover almost completely over a short period of time.