Environmental influences on reproduction in female giraffe were investigated by calculating conception dates for 123 calves and twenty foetal giraffe from the eastern Transvaal, South Africa. Of these, 60% occurred during the 4 months December to March. This period is the peak of the austral summer when plant leaf production is at a maximum, the preferred food species of the giraffe are abundant and the protein and energy content of these are high. Rainfall is also highest at this time. Conceptions also occurred in all other months of the year. Data on calving from captive animals in Australia, and from wild giraffe elsewhere in South and East Africa were also included in the study. Nineteen adult male giraffe collected over a period of 1 year from the eastern Transvaal were also investigated. Seminiferous tubule diameter fluctuated with age but regular seasonal fluctuation was not apparent. Testicular testosterone concentration varied from trace amounts to 10.1 μg/g. Testes mass and epididymes mass were closely correlated with age but no seasonal effects were apparent.