Limited numbers of melanophores and xanthophores exist in the skin and also inside the body of the ice goby, Leucopsarion petersii. These chromatophores show fundamentally identical fine structural features to those described in many other fishes examined hitherto. When the ice goby is adapted to a dark or white background, chromatosomes in the cells disperse or aggregate, respectively. Interestingly, the melanophores existing inside the body, namely, those in the peritoneum and those close to the vertebrae, are likewise responsive. Studies on chromatophores in the excised tissue pieces show that they are responsive to various agents known to affect chromatophores. Although the population of the chromatophores in the ice goby is much smaller than that of many other fish, these cells may bear functional significance in the strategy for survival.