Dystonia complicating homocystinuria is extremely rare in the absence of thromboembolic disease. We report a unique case of recurrent dystonia in a patient with homocystinuria secondary to pyridoxine-unresponsive cystathionine beta-synthase deficiency. Brain MRI was normal. Two biochemical markers for homocystinuria, homocystine and methionine, were markedly elevated during periods when our patient manifested dystonia. These findings suggest that accumulation of sulfur-containing amino acids may contribute to the pathophysiology of dystonia in patients with homocystinuria.