Abstract If the medical, social, and demographic effects of the Abortion Act are to be properly assessed, it is essential to have reliable estimates of the number of abortions illegally procured in Britain before the Act came into operation on 27th April 1968. There is, at present, no agreement on what this figure is likely to have been, and published estimates range from several hundreds of thousands down to about 15,000 a year. For example, in 1950, Dr Eustace Chesser published 'a most conservative estimate that the figure cannot be less than a quarter of a million every year',l though 100,000 was the figure most often quoted before the law was changed. And in a recent study of the first three years of the Act Mrs. Madeleine Simms, who was much concerned as General Secretary of the Abortion Law Reform Association at the time, has said that 'during parliamentary debates on the Abortion Act, the Home Secretary used this as his base-line figure'.2 Since this was upgraded in press reports of her article to 'the official figure used by the Home Secretary, for the number of criminal abortions each year was 100,000',3 it may be useful to recall that what Mr Roy Jenkins, who was then Home Secretary, actually said was 'perhaps as many as 100,000 illegal operations a year take place'.4 This was in the course of a speech supporting a Private Member's Bill upon which the government's collective attitude was one of neutrality, and which Mr Jenkins therefore very properly prefaced by saying 'I am speaking for myself, as I am entided to do, as is any other hon. member, and on my own responsibility'. So whether or not this estimate was correct, it plainly has no authority as 'the official figure' and, in fact, no official estimate ever does appear to have been published, either by the Home Office or by any other government agency.