Various kinds of thin film transistors (TFTs) with In-X-O (X= B, Mg, Al, Si, Ti, Zn, Ga, Ge, Mo and Sn) channel layer were studied using combinatorial technique. The channel layers were deposited by sputtering on unheated substrates and post annealing of TFTs was carried out at 300°C in air for 1 hour. Most of the In-X-O TFTs showed the switching behavior except for TFTs with In-Mo-O and In-Sn-O channel layer. High TFT performance is obtained in the case of In-Ge-O (μFE ∼ 6cm2/V-s, on/off ∼ 10 10), In-Zn-O (μFE ∼ 26cm2/V-s, on/off ∼ 1010), In-Si-O (μFE ∼ 3 cm2/V-s, on/off ∼ 109). The electron mobility of In-X-O shows inverse correlation with the electron effective mass, me, of X-O, except when X is a transition metal element.