We report a 50-year-old right-handed woman who, at age 20, was diagnosed to have homocystinuria presumably due to cystathionine beta-synthase deficiency. At age 40 years, involuntary movements developed insidiously, affecting her face, neck and upper limbs. During the next 10 years, involuntary movements progressed and she could no longer walk. Examination disclosed bilateral lens dislocation and marfanoid skeletal deformity. Muscle strength was mildly decreased in the right arm and bilateral legs. There was hyperreflexia in the right upper and bilateral lower extremities without Babinski sign. Muscle tone was mildly increased in the neck and bilateral upper extremities. She had persistent generalized choreic movements, dystonia affecting the face and neck, and resting and postural tremor in the upper limbs and tongue. A cranial CT scan showed an old low density lesion in the left frontal area. Involuntary movements in homocystinuria is rare and, to our knowledge, only 9 cases have been reported. This case was unique in that involuntary movements developed in the adulthood.