Previous studies from this Laboratory have shown that cerebellar Purkinje neurons (PN) in ageing, ethanol-fed Fischer 344 rats may have terminal dendritic segments that are longer than in control rats. They also showed that the longer terminal segments represented a toxic effect of ethanol on PN, because their increase in length resulted from an ethanol-induced deletion of other terminal dendritic segments and not from dendritic growth. The purpose of the present study was to determine whether this effect of ethanol was localized to specific lobules or was widely distributed within all lobules of the cerebellar vermis. Twelve-month-old male Fischer 344 rats were treated with a liquid ethanol diet for 48 weeks. Age- and weight-matched controls were pair-fed with an isocaloric control diet. Terminal dendritic segments in Golgi-Cox-stained PN in four groups of lobules in the cerebellar vermis of control and ethanol-fed rats were measured for treatment-related changes in length. Results from these measurements showed that ethanol-exposed PN with significantly longer terminal segments were present in all groups of lobules, i.e. they were widely distributed and not confined to specific lobules. Results from these measurements also confirmed in a large sample of neurons (40 neurons per rat) that the topologically distinct unpaired terminal segments were characteristically longer than the paired terminal segments in PN of control and ethanol-fed rats and that both types of terminal segments were longer in the ethanol-fed rats than in the controls.