Determination of the erythrocyte sedimentation rate in capillary blood can be of value in identifying neonates with infection. The normal values for the method described here range from 1 mm/l hour at 12 hours of age to 17 mm/l hour at 14 days of age. Most noninfected neonates with moderate to severe RDS or with other serious illness had values well within the normal range. Infected patients had marked elevations, and the majority of values returned to normal with clinical improvement. Coombs-positive ABO hemolytic disease was also responsible for elevated values. In about half of the infected patients the rise was not seen until 24 to 48 hours after clinical symptoms first appeared. The ESR can be useful in the nursery as a preliminary step in the laboratory evaluation of the sick neonate. Serial determinations may be of aid in identifying the infected infant when the results of bacteriologic cultures are obscured by antibiotic therapy.