The effects of corn pollen and aqueous leachates of pollen upon the radicle growth ofBidens pilosa, Cassia jalapensis, andRumex crispus are shown. Extractions of pollen with various solvents and methods were carried out so as to assess its active principle and its effect uponC. jalapensis. The preliminary steps to separate and identify the allelopathic compounds of the sonicated and macerated pollen extracted with methylene chloride are described. The strongest inhibitory effect was produced by the hexane fraction. The allelopathic effect of corn pollen upon the growth ofC. jalapensis in several substrates is shown. The possible structure of some of the active fractions is discussed as well as the possibility that the allelopathic potential of pollen might actually occur in nature.