In September, 1948, a scheme for paid sick leave was introduced for industrial workers in Govern ment employment. By this scheme an employee who is absent from work because of illness receives his full flat rate of pay for as long as 13 weeks in any year. National Insurance benefit and any further allowances from other Government sources are deducted from this pay. All employees are entitled to receive sick pay once they have completed 26 weeks' Government service. If an employee has had five years' Government service, he is entitled to a further 13 weeks' absence on half pay. No one may receive more than one year's sick pay in any four years. Absences of three days only are not paid ; absences of four days receive one day's pay, but if a man is absent for a period of five days or more he receives sick pay for the whole period of absence. A doctor's certificate is required as evidence of incapacity. After this scheme was introduced there was a sharp increase in sick absence. The increase was more than had been expected and was maintained into the year 1950. The scheme was to have been revised in September, 1950, but by June it was clear that too little was known about it, and in July, 1950, we were asked to make this investigation. In 1949 the sick pay scheme applied to some 330,000 employees in 42 Government departments : 275,000 were employed in the four largest depart ments, the Admiralty, the War Office, the Air Ministry, and the Ministry of Supply. We decided to confine the study, initially at least, to these four departments, and visited their headquarters to discover what information was already available. Their statistics revealed that recorded sick absence as a whole appeared to have doubled. By far the larger proportion of that increase was due to longer rather than to shorter absences, particularly to absences of four weeks or more. The increase of recorded sick absence was spread fairly evenly throughout the main disease groups. The increase was real ; that is to say it was not to any extent accounted for by a reduction in absences of other kinds. (For example, there was a slight reduction in absences recorded as casual absence , as is to be expected when there is greater incentive to produce a medical certificate, but this reduction was negligible when taken in relation to the total increase in sick absence.) There remained, however, several important questions which could not be answered by a study of headquarters statistics and made necessary a sample survey in industrial establishments. The questions we posed, and which are analysed in our results, were :?