During the first world war intensive research on toxic chemical compounds was carried out in all the belligerent countries. Much of this research had, and still has, a rather restrictedinterest, but the studies on organic compounds containing phosphorus and fluorine, initiated in this country by Dr Saunders and his colleagues, have had wide epercussions. Not only have they influenced studies in enzymology and even clinical medicine, but they have achieved industrial importance in the general field of pest control. The development of modern systemic insecticides, which stems from the independent wartime studies of Dr Saunders in England and Dr Schrader in Germany, is indeed a fascinating story and one which is less well-known than it should be. The veil of secrecy covering the early work and the rather piecemeal uncovering of it in the years following the war have caused many chemists and biologists to remain very ill-informed about the development of knowledge in the field of organic phosphorus and fluorine compounds. The present monograph should do much to remedy this state of affairs. Although intended primarily for chemists, the book contains much information on the pharmacology of the compounds discussed; this is particularly valuable since a proper appreciation of the biological background is essential to the chemist who wishes to see the work in proper perspective. As one who has had the privilege of following the work of Dr Saunders and his colleagues closely from its beginnings in 1939, I am particularly pleased that he has now written this authoritative account of it and I commend the monograph to chemists and biologists as a mine of information on one of the most interesting chemical developments which originated in work begun under the stress of war.