In 1947 the company with which the author is associated decided to institute an enquiry into the mortality of impaired lives. From the first the venture was both medical and actuarial, and a leading part in the planning of the investigation was undertaken by the company's Principal Medical Officer, T. W. Preston, M.D., who devised an impairment coding scheme and has since continued to supervise the coding of policies qualifying for inclusion in the data. While the present paper describes methods used in the statistical analysis of the results, the author wishes to place on record the major role played by Dr Preston in the carrying out of the investigation. The work has, in fact, involved the combination of medical and actuarial skills, and without the participation of the medical profession no actuarial investigation into the mortality of impaired lives would be practicable.