Chediak-Higashi Syndrome is an autosomal recessive disorder, characterized by the presence of large intracellular granules, particularly lysosomes and melanosomes. While the Chediak-Higashi Syndrome is a rare disorder in humans, phenotypically similar syndromes are found in other species. Fusion of normal fibroblasts to Chediak fibroblasts complements the Chediak disorder, restoring normal lysosome size and distribution. Fusion of wild-type with Chediak fibroblasts from human, mouse, or mink demonstrates that wild-type fibroblasts can complement any of the Chediak fibroblasts. Complementation was not observed in interspecific hybrids between Chediak fibroblasts from these species, suggesting that the same gene product is defective in humans, mice, and mink.