The study of the behavior of electronic states in thin films is quite interesting from the following point of view, that one can study and understand the remarkable scaling theory predictions in the cross over from two to three dimensions and to look at whether physical picture of interference due to scattering of Bloch states from the impurities is adequate in the more general situation. The role of film thickness in metal insulator transition (MIT) is investigated numerically using finite size scaling and transfer matrix methods. Self-consistent theory is being used to treat this problem and extended the theory to thin films. We also examine the criteria of the phase transition in the presence of magnetic field (B) by investigating critical behavior of localization length and conductivity around MIT line in (B, localization length) plane. Furthermore, we also investigated MIT induced by various other parameters such as inelastic coherence length, temperature, magnetic field andfilm thickness.