The molecular diffusivities of benzene, toluene, naphthalene, acenaphthylene, phenanthrene, anthracene, benz[a]anthracene, pyrene, and benzo[e]pyrene were measured in air at temperatures ranging from -5 to +40-degrees-C using a modified arrested flow method. Molecular diffusivities in air for all compounds studied decreased with molecular size, and increased logarithmically with temperature. The experimental data have been used to formulate a predictive equation for the estimation of molecular diffusivities of aromatic chemicals in air as a function of temperature and molar volume.