Nine hundred and sixty-seven men who were employed in a nickel refinery in South Wales on at least two occasions five or more years apart before 1945 have been followed up, and the mortality rates from different causes related to the date of their first employment. Previous reports suggested that the occupational risks of lung and nasal sinus cancer had been eliminated by 1925. It is now shown that the risk persisted until 1930, which accords better with the temporal changes in the process.