A total of 124 blood samples obtained from newborn infants have been analyzed using two different blood counters: S+2 (Coultronics) and H1 (Technicon). Correlations are found to be good between the two different groups of results for most of the parameters. However, white cell counts are wrong in 60% of the cases as assessed by one of the H1 channels, probably because red blood cell lysis was not complete. Differential analysis of nucleated blood cells was less satisfactory as illustrated by: 1) the high incidence of rejections (50% for S+2, 60% for H1); 2) the low sensibility of both analysers for erythroblastemia; and 3) and on the H1 for circulating immature granulocytes. Alarms were frequent leading to the realization of a differential on blood smears which avoided incomplete or false results but was time consuming. Samples from newborn infants have still to be analyzed on an individual basis and cannot enter the overall daily treatment of samples from adults or children.