The capacity of the α isomer of retinyl acetate to support growth in hamsters fed a vitamin A-deficient diet was assessed over a 40-fold dose range. Although decreased relative potency of the α isomer, as compared with the β isomer, was found, sustained weight gain and survival for 6 months were achieved with a weekly intraperitoneal dose of 300 µg of the α isomer. An intraperitoneal dosage of α-retinyl acetate resulted in greater activity than an oral dosage.