New citrus rootstocks were developed by sexual hybridization and evaluated for vigor, health, uniformity from seed, and resistance to disease. Hybrid rootstocks with favorable combinations of traits were budded with common scions and established in replicated field trials along with standard rootstocks at several locations for evaluation of effects on tree health, tree size, fruit quality, and yield. Significant differences were observed in performance of different rootstocks. One new USDA hybrid rootstock, HRS-812, produced healthy standard-size trees with excellent yields in Florida trials with 'Valencia' (Citrus sinensis [L.] Osbeck) and 'Ambersweet' orange, 'Fallglo' citrus hybrid, and 'Sunburst' mandarin (C. reticulata Blanco) scions and appeared resistant to tristeza virus. Rootstock trials at two locations in Puerto Rico with 'Dancy' mandarin and 'Chironja' scions on HRS-812 rootstock gave good tree growth and excellent yields. The information collected in these trials can be useful in selecting rootstocks for new plantings of citrus.