1. The objective of this study was to determine hens' sperm storage potential. 2. Efficient duration (De, number of days between insemination and the first clear egg), maximum duration (Dm1, number of days from the day after insemination to the last fertile egg before two consecutive infertile eggs) and maximum duration (Dm2, number of days from the day after insemination to the last fertile egg) of fertility, fertile egg number, egg production, laying rate and fertility during the 24 d following the latter of two inseminations (with 1 x 10(8) spermatozoa) on two consecutive days were measured in a total of 150 dual-purpose hens at 30 weeks of age. 3. De, Dm1 and Dm2 were 12.06, 14.44 and 16.17 d, respectively, and the three definitions of fertility duration (DF) differed greatly. 4. Significant correlation coefficients between De and Dm1, Dm1 and Dm2, and De and Dm2 were 0.51, 0.57 and 0.23, respectively. 5. We suggest that De and fertile egg number should be used to assess the ability of storing spermatozoa in female fowl.