The five-year summary of results of a trellising tria1 with ‘Thompson Seedless’ vines grown in the San Joaquin Valley showed that a wide, four- wire double crossarm trellis increased vine growth by 38 percent, crop yields by 20 percent, and soluble solids by nearly 3 percent, when compared with a one-wire trellis. When a two- wire single cross-arm trellis was compared with a one- wire trellis the gain in vine growth was 14 percent, yield was enchanced by 13 percent, and soluble solids were the same.