PbTe is a semiconductor with a direct band gap in the L point of the First Brillouin Zone (FBZ) of about 0.2 eV. This semiconductor has been studied in the past decades because it is an important technological material for infrared devices. In this work, the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method has been used in order to study the phase transitions of PbTe. This gives us an idea of the behavior of the electronic structure of the compound under pressure. The study was carried out using the cohesion energy as function of the unit cell volume in both NaCl and CsCl structures. We have examined if a phase transition between these structures is possible. We have obtained a phase transition pressure of 7 GPa, in good agreement with experimental data. We calculated the band structure and the density of states at equilibrium volume of the above mentioned structures. Also, the band structure was calculated at a point immediately before and another after transition. We compare the electronic structure between these points. We found no gaps for the CsCl structure and the material exhibits a metallic behavior. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)