The band inversion in the PbSnTe compound has been observed by optical and electrical measurements. The samples, high quality Pb 1Ϫx Sn x Te epitaxial layers, have been grown by molecular-beam epitaxy on ͑111͒BaF 2 substrates. Optical transmission measurements have revealed a change in signal of the energy gap temperature derivative for samples with 0.35ϽxϽ0.70. In the same samples and at the same temperature, a minimum in the resistivity has been observed, showing a interrelation between the optical and electrical measurements. However, the temperature, for which the inversion occurs, is not that predicted by the band inversion model. This discrepancy is supposed to be due to the relatively high hole concentration of these samples.