Various defects in leukocyte function have been reported in Chédiak-Higashi syndrome (CHS); however, to our knowledge, lymphocyte locomotor capacity has not been investigated. A 7-year-old boy with typical signs and symptoms of CHS showed impaired neutrophil, monocyte, and lymphocyte locomotion. Chemotaxis studies were performed by the micropore filter technique using modified Boyden chambers, and migration was measured by the leading front method. Treatment with ascorbic acid (vitamin C), 500 mg/day for five days, resulted in a significant increase in in vitro neutrophil and monocyte chemotaxis but failed to affect lymphocyte locomotion.