The aim of this study — qualitative and quantitative evaluation of synaptogenesis in the developing cerebellum of the rat (postnatal Days 2–45) using immunohistochemical detection of synaptophysin (SYP) as the the marker. The expression of SYP was demonstrated in postmitotic neurons of the external granular layer and migrating precursors of granular neurons of the cerebellum. During the whole period studied, an increase in the width of the zone of synaptogenesis in the molecular layer took place together with the decrease of SYPimmunoreactivity. The reduction in the number of SYP-immunopositive synapses was noted around Purkinje cell perikarya from Day 7 till Day 15. In the internal granular layer, SYP-immunopositive dots were observed that increased in size from Day 2 to Day 45 due to the formation of cerebellar glomeruli. In the cerebellar interposed nucleus, the number and sizes of axosomatic synapses around neuronal perikarya were found to increase during the whole period examined. In the neuropil, the uneven aggregates of SYP-immunopositive axodendritic synapses were observed.