In the present review I am starting with the year 1947 because, apart from the early Russian experiments which have been well reviewed in previous papers, this year saw the first field-scale trial of which published details are available. This trial, made at Gorgas, Alabama, has been followed by continuous programs of research in this country and by others in Belgium, Britain, France (French Morocco) and Italy. Each group of investigators has proceeded along lines dictated by its own interests and so the subject has been studied from a wide viewpoint. Each has had as its objective, the determination of the technical economic feasibility of the process of gasifying coal in place. Collaboration has been maintained between the teams during the course of the work and much useful information has been exchanged.