The effect of phytohormones, light and phosphate on in vitro production of ubiquinone 10 from the suspension cultures of Nicotiana tabacum cv. Xanthi callus was investigated. The inoculum size and cultured time in the suspension culture had to be at least over 2 % of medium volume at 15 days for the excellent growth of Xanthi callus. The growth of Xanthi callus in the suspension culture was improved by addition of NAA and 2,4-D, especially NAA 1.0mg/1 alone, at the light condition. The optimal concentration of phytohormone was 0.1 mg/l 2.4-D and 1.0 mg/l NAA for productivity of ubiquinone 10 in the suspenseion of Xanthi callus. Addition of 3mM KH$_2$PO$_4$ to the medium was more effective in promoting ubiquinone-l0 formation than other concentration in the light condition. Content and production of ubiquinone-l0 in the suspension cultures of Xanthi callus were the highest at the MS media containing 0.5mg/L kinetin, 0.5mg/L 2,4-D, 1.0mg/1 NAA, 3mM phosphate and 2 % inoculum in the light.