Nevirapine (11-cyclopropyl-5,11-dihydro-4-methyl-6H-dipyrido[3,2-b:2',3'e][1,4]diazepin-6-one) is an antiretroviral drug belonging to the class of the non-nucleoside inhibitors of the HIV-1 virus reverse transcriptase. As most of this kind of antiretroviral drugs, nevirapine displays a butterfly-like conformation which is preserved in complexes with the HIV-1 reverse transcriptase. In this work, we present a detailed vibrational spectroscopy investigation of nevirapine by using mid-IR, near-IR, and Raman spectroscopies. These data are supported by quantum mech. calcns., which allow us to characterize completely the vibrational spectra of this compd. Based on these results, we discuss the correlation between the vibrational modes and the cryst. structure of the most stable form of nevirapine.