Mercury, arsenic, and antimony were determined in marine sediments collected from Kagoshima Bay, and their distribution was investigated. The contents of mercury, arsenic, and antimony in surface sediments were higher than those in the marine sediments of the open ocean. The average contents of mercury, arsenic, and antimony in surface sediments in the northern part of the bay were higher than in the southern part. The high-temperature sediments (about 200 °C) in the vicinity of a sea bottom fumarole, located at a depth of about 200 m in the northern part of the bay, showed abnormal concentrations of mercury, arsenic, and antimony derived from the fumarole gas; the contents of these components decreased sharply with an increase in the distance from the fumarole. A high degree of positive correlation was found among the contents of the three components (mercury, arsenic, and antimony) over the northern part of the bay. In contrast, no such correlation was observed in the southern part of the bay. This is in accord with the fact that volcanic activity is more vigorous in the northern than in the southern part of the bay.