A population of Plantago lanceolata (ribwort plantain) from a roadside was found to have higher Pb tolerance than populations away from the roadside; this reflected the sharp differences in Pb content of the soil and the plants at these sites. Tolerance tests on seedlings showed that the Pb tolerance was transmitted to seed progeny. Cynodon dactylon (Bermuda grass) showed generally a higher Pb tolerance than P. lanceolata, but there was no evidence of a greater Pb tolerance of the roadside population when compared with populations from control sites. These results suggest that the Pb level found at the roadside was sufficiently high to impose selection pressure for the evolution of tolerance in a sensitive species, but no overt effect was seen in a species with a greater inherent tolerance. This provides another example of rapid and highly localized evolutionary change in plants.