The fluorescence spectral method was employed to assay benz(a)pyrene (BP) level in medicinal herbs, growing along country roads in Leningrad Province, versus volume of traffic and proximity of roads. In some areas, BP levels in herbs, growing near roads were found to be scores of times the background value (0.3-4.5 micrograms/kg air-dry specimen). A correlation between BP level and proximity of roads held in a 50 m-wide zone. Raised levels of BP in herbs picked in that zone were determined by the morphological features of species and volume of traffic.