Previous research indicated that Raphanus sativus L. `Chinese Radish Jumbo Scarlet' (CJRS) has an obligate vernalization requirement for flowering and can be vernalized as an imbibed seed in less than 10 days at 6 °C. For these reasons, it serves as an excellent model system for vernalization studies. This study was initiated to gain an understanding of the interaction between cold duration, exogenously applied GA3, and photoperiod on R. sativus CJRS flowering. R. sativus CJRS seeds were sown in 90-mm petri plates on Whatman no. 1 filter paper saturated with plain water or a solution containing 10-5 M or 10-3 M GA3. After germination (i.e., when the radicle was visible), seedlings were either directly transplanted into 10-cm pots and placed in a greenhouse, or transferred to another petri plate onto filter paper saturated with water only and placed in a growth chamber at 6 °C (75 μmol•m-2•s-1 for 8 h) for 2, 4, 6, 8, or 10 days. Greenhouse conditions were: 20 °C, ambient light (December to January, St. Paul, Minn.) plus 70 μmol•m-2•s-1 supplemental light (high-pressure sodium lamps, 0830-1630 hr), under either an 8-h photoperiod (covered with opaque cloth from 1630-0830 hr), or ambient photoperiod plus night-interruption lighting (2 μmol•m-2•s-1, using incandescent lamps, 2200-0200 HR). Results will be presented.