SUMMARYAn account is given of 195 cases of pneumonia and bronchopneumonia in children from 0 15 years of age, treated in the medical wards of Kronprinsessan Lovisas Barnsjukhus during the period ½ 1941 ½ 1945.In all the cases chemotherapy has been given in the form of a massive single dose. In 48 cases (24 %) the massive dose treatment has been supplemented by continuous chemotherapy. Sulphapyridine, sulphathiazole and sulfadimin have been used. The dosage has been 0.3 g per kg body weight for children under 3 years, and 0.2 g per kg body weight for the others, with 8 g as the maximal dose.There have been few complications, and the toxic side‐effects have been extremely slight. 5.6 % fatal cases are recorded of all the cases observed, but if those cases where pneumonia has appeared as a complication of a serious congenital malformation or of a serious primary basic illness, are subtracted, the mortality is 2.1 %.As the massive single‐dose treatment is technically easy to carry out, gives the patient more repose than does the continuous treatment during the period when the illness is most severe, lessens to a considerable degree the work of the hospital personnel, gives a result which can be compared favourably with that of continuous chemotherapy, gives rise to few complications and toxic side‐effects, this treatment can be recommended for pneumonia in children.Satisfactory results have also been obtained with massive single‐dose treatment in eases of capillary b