Treatment of pneumococcic pneumonia with type-specific antipneumococcus serum has received wide attention.1"Adequate" treatment is said to hasten recovery and improve the outcome. Three major factors determine the "adequacy" of serum: the duration of the untreated disease, the total amount of serum given and the rapidity of its administration. It is reasonable that these factors are interdependent in such a way that the relations between them are quantitative and amenable to analysis. MATERIALS AND METHODS2 In the preceding articles3certain data have been presented concerning all (1,469) patients with typed pneumococcic pneumonia treated in the Los Angeles County Hospital during the five year period 1934 to 1938. Of these, 569 received specific serum therapy, but 56 cases were discarded because the records were inadequate. The remaining 513 are otherwise unselected. All patients received commercial type-specific, horse or rabbit antipneumococcus serum intravenously, in various hospital services, at the order