The nuclei of the locus coeruleus and subcoeruleus were examined in human brains from individuals of 14 to 87 years. Serial counts were performed on every tenth Nissl stained paraffin section of melanin containing cells within the entire length of these nuclei. After 63 years, the neuronal population in these nuclei decreased 40%. This significant decrease in cell number is the first reported for a brain stem structure. In view of the relation of these noradrenaline containing cells to the catecholaminergic system and the widespread projections between these nuclei and other central nervous system structures, this decrease may be a factor in alteration of some central nervous system activities with increasing age.