A new and efficient stereological method for estimating the total number of the different cell types in rat cerebellar cortex is presented. The cells have been subdivided into the following categories: Purkinje cells, granule cells, Golgi cells, glial cells in the granular layer, Bergmann glial cells and neurons and glial cells in the molecular layer. The method has been used to estimate the total number of some of the cell types in rats exposed to orally administered toluene at doses of 200, 400 and 800 mg/kg/day for 12 weeks compared with a control group. No statistically significant differences were found between the exposed and non-exposed animals. The described method can be used in a number of both biological and experimental studies. With the use of new stereological methods it is possible to get precise estimates of total cell numbers in a much shorter time than earlier required. This makes it possible to improve the reliability of the final result by increasing the number of cases processed.