The a.c. conductivity of Langmuir-Blodgett multilayers of ytterbium bisphthalocyanine has been measured in the frequency range 10-10(6) Hz and for temperatures from 20 to 60 degrees C. The effects of two common atmospheric pollutants, nitrogen dioxide/dinitrogen tetroxide (NOX) and tobacco smoke, on the complex impedance of the material have been analyzed in terms of the Havriliak-Negami model for conduction.