Allelopathy involves both inhibitory and stimulatory biochemical interactions between plants. The phenomenon has received great attention since the 1980's all over the world; however, in Turkey, research on allelopathy just started in the late 1980's. Studies have been done with many crops, trees, shrubs and weeds under both laboratory and field conditions to determine their allelopathic potential and its use for weed control. Crops belonging to the Brassica family are the most studied species for allelopathic potential to control weeds. Among the Brassica species, garden radish (Raphanus sativus) has been most studied to control johnsongrass (Sorghum halepense). Allelopathic activity of alfalfa (Medicago sativa) also received some attention. The role of allelopathy in weed interference on crop production was also studied. In conclusion, allelopathy studies should parallel with contemporary studies such as ecological and chemical studies, and an integrated approach should be adopted to fully utilize the applicability of allelopathic plant species to control problem weeds.