In the multicellular tissue, cell-cell interaction is important for a precise control of its function. The exchange of signaling molecules between adjacent cells via connexon allows the functional harmony of cells in the tissue. The present research was to determine the presence and expressional patterns of connexin (Cx) isoforms in the rat epididymal fat during postnatal development using quantitative real-time polymerase chain reaction (PCR) analysis. Of 13 Cx isoforms examined, expression of 11 Cx isoforms in the epididymal fat during postnatal development was detected. These Cx isoforms include Cx26, Cx31, Cx31.1, Cx32, Cx33, Cx36, Cx37, Cx40, Cx43, Cx45, and Cx50. Expressional levels of all Cx isoforms at 1 and 2 years of age were significantly higher than those at the early postnatal ages, such as 7 days, 14 days, and 24 days of ages. Except Cx33 and Cx43, the transcript levels of rest Cx isoforms at 1 year of age were significantly lower than that at 2 years of age. In addition, expressional patterns of Cx isoforms between 7 days and 5 months of ages generally varied according to the isoform. The existence of various Cx isoforms in the rat epididymal fat has been identified and expression of each Cx isoform in the epididymal fat during postnatal development has shown a particular pattern, distinguishable from the others. To our knowledges, this is the first report showing expressional patterns of Cx isoforms at transcript level in the epididymal fat at various postnatal ages.