Single crystals of Bi2Sr2CaCu2Ox have been grown by directional solidification method in order to analyze annealing effects on critical superconducting temperature (T-c) by AC susceptibility measurements. Structural modifications were studied by X-ray diffraction. A decrease of the transition width was observed in samples treated in oxygen or argon atmospheres at 500 degrees C for 10 h. Higher T-c values were obtained for argon annealings. The magnitude of T-c changes and its correlation with c lattice parameter is found to be sample-dependent.