The central 95 percentile estimates of the normal white cell types (as determined by a standard differential count) were calculated from 777 normal individuals. The results were divided into groups by age and sex and expressed both as percentages and as absolute numbers of cells.A similar survey was made using the prototype of a new automated differential counting method (Hemalog-D(TM)). The two sets of laboratory values showed no statistically significant differences regarding age or sex and were strikingly similar in most cell types with the exception of band and juvenile forms of granulocytes. As expected, the normal range using the manual technique was somewhat broader than that found with the automated method. In addition to being the first comparison of machine counts with visual differentials this study provides additional insight into the age distributions of normal cells.