The stability properties of ion temperature gradient instability are studied analytically in both weak and strong ballooning limits for toroidal geometry. Numerical solutions of the eigenmode equation are also obtained. The corresponding local ion anomalous thermal conductivity chi i estimated from linear results is consistent with those given by Connor (1986), and Lee and Tang (1987) in slab geometry. The toroidal effects contribute the additional Pfirsch-Schluter factor (1+2q2)34/.