The purpose of this study was to determine whether the observed swelling of smooth endoplasmic reticulum (SER) profiles in Purkinje dendrites in our old ethanol-fed F344 rats: (1) represented measurable dilatation, (2) was present in dendritic shafts and spines, and (3) was reversed following recovery from ethanol. Of the 45 rats in 3 treatment groups (chow-fed, pair-fed, and ethanol-fed), 30 rats were euthanized after 40 weeks, and 15 were maintained on rat chow for an additional 20-week recovery period. Electron microscopy of cerebellar preparations was used to analyze morphological alterations in SER profile size within the dendritic shafts and spines of Purkinje neurons. Results showed significant SER dilatation following 40 weeks of ethanol consumption, which disappeared after ethanol withdrawal.