The total leucocyte count was measured in 480 old people living at home, and differential counts carried out in 468. The total leucocyte count and the absolute polymorph and lymphocyte counts were found to have a lognormal frequency distribution, the differential counts a normal distribution. The range of total leucocyte counts was 3100–8900/mm3, of polyrnorph counts 1800–6500/mm3, and of lymphocyte counts 700–3500/mm3. Comparison with published data suggests that old people have a tendency to leucopenia, due to lymphopenia.