This inquiry embraces the seventeen years beginning with 1878 and ending with 1894, the material utilised being the weekly mortality returns published by the Registrar-General for Scotland. Particulars are given in these returns of the number of deaths from small-pox, measles, scarlet fever, diphtheria, whooping-cough, diarrhœa, fever, croup, laryngitis, bronchitis, pneumonia, and pleurisy. Some of the diseases are classed together, viz., typhus and typhoid fever, croup and laryngitis, and bronchitis, pneumonia, and pleurisy. The data discussed also embraces returns of deaths from all causes, deaths of infants under one year of age, and of persons aged sixty years and upwards. The deaths have all been entered as having occurred during the calendar weeks in which they were registered, but as notification usually follows decease by several days, a slight element of error is introduced. Since the returns do not give any information as to the duration of the illness, we are unable to ascertain whether specific weather types are in casual relationship to disease. There are every week a number of deaths from uncertified and unspecified causes. These omissions are subsequently rectified, but their presence in the returns does not affect the general results of the investigation. It is our intention merely to discuss some of the broader results of the inquiry, the chief object of which is to give a first approximation to the seasonal death-rate of the diseases under review. In discussing the relation between weather and disease, it is well to keep in mind the fact that different diseases exhibit varying degrees of sensitiveness to weather influences, and that climatic changes take some little time to affect the human subject.