Morphological transformation of lectin-positive microglia/macrophages in the developing rat cerebral hemisphere was analysed using quantitative methods. During the first postnatal month, the cells showed increases in their size and fractal dimension accompanied by a simultaneous decrease in their solidity. Regional variations in dynamics of the process indicated the existence of spatio-temporal developmental gradients within the cerebral hemisphere wall which might correspond with regional patterns of neuronal differentiation. Results of the present study prove that the quantitative methods can be the source of reliable data replacing subjective cell typologies.