Many-day rhythms of proliferative activity of the corneal and esophageal epithelium and serum corticosterone levels were studied in adult male Wistar rats. We detected a 4-day rhythm of proliferative activity of esophageal epithelium negatively correlating with corticosterone level. A more pronounced decrease in the number of mitoses in the esophageal and corneal epithelium was recorded every 12 days. Analysis of the rhythm of mitotic activity in different experimental series carried out over 9 months showed that the acrophase of the detected 4- and 12-day periods is shifted 1 day forward every 69-73 days. The detected infradian constituents of the circadian rhythms of epithelial proliferative activity should be taken into consideration in experimental studies and in development of chronobiological approaches to the treatment of diseases caused by disorders of the proliferative activity of the epithelium.