Unfertilized rainbow trout eggs were kept at 2 ± 1°C under O2, CO2, N2, air or expired air. Eggs were stored either loose or sealed in PE foil. After 5, 10, 15 and 20 d the pH was recorded and the eggs were fertilized with cryopreserved semen and incubated to the eyed egg stage. Under CO2 eggs succumbed within 1 d. Between air and exhaled air there was no difference. With loose eggs air was preferable to O2 or N2. Under all conditions PE foil improved fertilization rates. Enveloped in PE foil unfertilized rainbow trout eggs could be stored at 2 ± 1°C for up to 3 weeks under O2, air or anaerobic conditions, retaining a fertilization capacity of 40 to 59%.