The occasional passage close to New Zealand of ships carrying nuclear materials is a continuing source of controversy in the country. This arises partly from inherent antinuclear sentiment and partly from a concern that an accident with one of these shipments could result in serious damage to the environment. The article describes the nature of these nuclear cargoes, explains the context within which they take place and examines the various risk scenarios that have been envisaged. It is argued that the actual risk probability for the sorts of accident that have been envisaged is so small that they need not be of concern and that further action on the part of the New Zealand Government in the way of protesting to Japan or the shipping companies, or demanding further safeguards and indemnification, is unnecessary.