Direct communication between neighboring cells through connexin (Cx)-based gap junction is a crucial biolo– gical manner to regulate functions of a tissue consisting of multi-cell types. The present research evaluated expressional changes of Cx isoforms in the caput epididymis of adult rat exposed to estradiol benzoate (EB) or flutamide (Flu) at the early postnatal age. A single subcutaneous administration of EB at a low-dose [0.015 g /kg body weight (BW)] or a high-dose (1.5 g/kg BW) or Flu at a low-dose (500 g/kg BW) or a high-dose (5 mg/kg BW) was performed to an animal at 1 week of age. Quantitative real-time PCR analysis was employed to determine expressional changes of Cx isoforms. The transcript levels of Cxs30.3 and 37 were decreased by a low-dose EB treatment, while decreases of Cxs31, 31.1, 32, 40, and 45 transcript levels were observed with a low-dose EB treatment. The treatment of a high-dose EB resulted in expressional reduction of Cxs30.3, 31, 31.1, 37, 40, 43, and 45. The Flu treatment at a low dose caused increases of Cxs26, 37, and 40 transcript levels but decreases of Cxs31.1, 43, and 45 transcript levels. Increases of Cxs30.3, 31, 37, and 40 mRNA amounts were induced by a high-dose Flu treatment. However, exposure to a high-dose Flu produced expressional decreases of Cxs31.1, 32, and 43 in the adult caput epididymis. These observations suggest that exposure to EB or Flu at the neonatal period could lead to aberrant expression of Cx isoforms in the adult caput epididymis.