This report presents the results of an investigation into the mortality of impaired assured lives during the period 1947-63. A preliminary account, outlining the nature of the investigation, was given by the first author in his Presidential Address to the Assurance Medical Society in 1955, and a report on the results up to the end of 1958 was given in a paper by the second author, which was presented to both the Institute and the Faculty of Actuaries in 1961 (J.I.A. 87, 196, and T.F.A. 27, 20). Earlier this year the first author read a paper to the Assurance Medical Society which gave the statistical results up to the end of 1963. These same statistics form the basis of the present paper, but the text has been revised and expanded. Certain passages in the present paper, notably §§ 7, 8, 9 and 11 which describe the recording and tabulation of data, have been reproduced from Clarke's 1961 paper.