A knowledge of the age, sex and seasonal incidence of many diseases of childhood is of considerable diagnostic value. We have been unable to find in the literature any recent statistics on all three aspects of the subject. Accordingly, the records of nearly 2,500 patients from birth to 13 years of age who were admitted to the Hospital for Sick Children during the past five years and about 5,000 records obtained from the Toronto Department of Public Health have been examined. The results are tabulated in tables 1 to 5. We fully realize in regard to the hospital records that certain of the diseases considered may be encountered in private practice at slightly different age limits. For example, the youngest patient admitted to the hospital with asthma was 1 year of age, while in private practice we have seen mild cases in children from 4 to 5 months of age.