The Transportation Safety Act of 1974 has increased the responsibilities of the National Transportation Safety Board (NTSB) in the investigation of marine accidents. Major marine accidents and certain accidents involving public vessels are investigated in accordance with joint regulations between the U. S. Coast Guard and NTSB. The Safety Board is required to determine the cause of those accidents and to make safety recommendations. The paper discusses how NTSB's role in marine safety evolved, the investigation of marine accidents, and the processing of safety recommendations. Some selected accidents and safety recommendations are discussed.