Estimates of total number of different neuron and glial cell types in the dentate nuclei and the four major regions of the human cerebellum were obtained by new stereological methods. With the optical disector and Cavalieri methods, the total number of neurons and glial cells in the human cerebellum of five elderly men was estimated to be 105,000 x 10(6) (coefficient of variation, CV = 0.13). Of this total, the granule cells comprised 101,000 x 10(6) (CV = 0.13) and the Purkinje cells comprised 30.5 x 10(6) (CV = 0.13) of the neurons. The mean of the total number of neurons in the dentate nucleus was 5.01 x 10(6) (CV = 0.28). The average surface area of the human cerebellum was estimated to be 1160 cm2 (CV = 0.29). The rationale for the different sampling schemes used to quantify the various cell types is described.