The actuarial aspects of the liability of the employer towards his employees in respect of industrial accidents and diseases have not been discussed frequently at the Institute, and the comparatively small number of contributions to the Journal on this subject is doubtless to be attributed, in no small measure, to the difficulty of obtaining access to any considerable body of data bearing more particularly upon the duration of compensation claims. Some three or four Tears ago the author was asked to investigate the experience of a Colliery Owners' Mutual Indemnity Fund, and although the investigation deals with a single industry and relates to a period somewhat remote, it is hoped that, in so far as it may throw some light upon a subject regarding which but little information has as yet become available, the following account of the methods followed, and the results obtained, may nevertheless be of interest and possibly of some value. The author desires to express his indebtedness to the directors of the fund, which for certain reasons it is not desired to name, and which is hereafter referred to as “the Fund,” for their courteous permission to utilize in this manner information obtained in his professional capacity.