The effect of pre- and postnatal photoperiod on testicular development in albino rat was investigated in the present study. It was found that testicular maturation is directly proportional to the length of both pre- and postnatal photoperiods. Although the earliest signs of degeneration of the seminiferous tubules appeared following the exposure to short prenatal photoperiod, yet compensation and improvement of these effects has occurred with exposure to longer photoperiod postnatally, specifically effective with moderately short prenatal photoperiod. Failure of production of spermatozoa resulted after exposure to short photoperiod both pre- and postnatally.