Aquaporin 1 (AQP1) is one of the water channel proteins localized on membranes of various cells including reproductive organs. Although expression of AQP1 was reported in both testis and ovary by reverse transcription polymerase chain reaction (RT-PCR), protein expression of AQP1 has been not demonstrated yet. Moreover, it is still controversial whether AQP1 is expressed or not in male and female gametes. The aim of this study was conducted to detect AQP1 protein by westernblotting in pig sperm and oocytes. Porcine cumulus oocytes complexes (COC) were cultured in maturation media (NCSU37 supplemented with 10% porcine follicular fluid, 0.5 μg/ml FSH and 1.0 IU/ml LH) up to 48 h and collected every 12 h. After collection, these COCs were denuded and extracted. Ejaculated boar spermatozoa was collected and then homogenized in Laemmlli sample buffer. These extracts were used for SDS-PAGE using 12.5% polyacrylamide gel. Two kinds of polyclonal antibodies (each antibody recognizes c-terminus and middle part of canine AQP1) were used for the detection of porcine AQP1. In sperm, westernblotting showed a 28-kDa band which corresponds with the molecular mass of AQP1 reported in other species. Also in oocytes, AQP1 was already expressed abundantly in oocytes collected immediately after recovery. The expression level was not changed during in vitro culture, but the migration of the band was observed in oocytes cultured for 48 h. Both antibodies of c-terminus and middle part could detect the same band. From these results, we demonstrated for the first time the immunodetection of AQP1 in sperm and oocytes of pig. Our data also suggest a possibility that AQP1 in oocytes may be regulated by factor(s) during in vitro maturation.