Technical Abstract: Primocane-fruiting blackberries may offer opportunities for season extension and off-season fruit productionivation. ‘Prime-Jan’® plants were established at the Oregon State University - North Willamette Research and Extension Center, Aurora, Ore. (NWREC). Half of the planting was established under a high tunnel and the remainder planted in an open field. Primocanes were subjected to 4 pruning treatments: 1) re-cut to just above the crown once reaching 0.25 m, then soft-tip the subsequent canes at 0.5 m; 2) re-cut at 0.5 m, then soft-tip at 0.5 m; 3) double-tip canes (soft-tip main cane at 0.5 m, then soft-tip branches at 0.5 m); and 4) soft-tip the main cane at 0.5 m (control). Plastic was placed on the top of the tunnel from 5 Sept. 2006 and 31 Aug. 2007 until the end of harvest to protect fruit from weather. Fruit harvest began on 12 Sept. in the open field and tunnel, but lasted about 3 weeks longer in the tunnel, ending on 16 Nov. Primocanes that were double-tipped had nearly twice the flowers and fruit than canes that were soft-tipped only once. In the tunnel, cumulative yield of double-tipped primocanes averaged 10.7 t·ha-1 in 2006 and 19.3 t·ha-1 22 in 2007. On average, cumulative yield for double-tipped primocanes was 47% less in the open field than in the tunnel. Harvest was not delayed in canes that were re-1 cut at 0.25 m in 2006, compared with the control and the double-tipped treatment; however, harvest was delayed by 2 weeks in 2007 in this treatment. In contrast, harvest was delayed by about 4 weeks when primocanes were re-cut at 0.5 m. Primocanes that were double-tipped produced heavier fruit than other pruning treatments – 33% heavier than the control, on average. Double-tipped primocanes did not have more ovules per flower, but had significantly more drupelets set compared to the control. In addition, plants growing under the tunnel tended to produce heavier fruit than those grown in the open field. Although fruit under the tunnel was protected from rain, TSS, pH, TACY, and total phenolics began to decline in late October in both years, likely due to cool night temperatures and low light conditions.