During the past year, a study has been made of the sedimentation rate of the red blood cells in children, with a view of obtaining information which might be of practical clinical value. A study of the literature on the sedimentation reaction reveals a comparative scarcity of reports concerning pediatrics;1 the majority of communications pertain to gynecology and obstetrics2 and to tuberculosis.3 The history of the development of the sedimentation reaction begins with observations made by Galen, Hewson, Hunter,4 Biffi5 and others. In 1897, Biernacki6 proposed a method for determining the sedimentation reaction and reported clinical and experimental observations. Fahraeus7 proposed another clinical method in 1918. Westergren8 modified the procedure in 1920 and subsequently, Linzenmeier proposed a simplified procedure9 and has added a micromethod.10 Many other modifications of the technic and new methods have been offered,11 all based on