ALLELOPATHY IS THE DIRECT OR INDIRECT USEFUL OR HARMFUL EFFECTS OF ALLELOCHEMICALS OF ONE PLANT ON OTHER PLANTS. IN ORDER TO STUDY THE ALLELOPATHIC EFFECTS OF RYE (SECALE CEREALE) ON WIMMER RYEGRASS (LOLIUM rigidum gaudin), LESSER CANARYGRASS (PHALARIS MINOR RETZ.), CHARLOCK MUSTARD (SINAPIS ARVENSIS L.), MILK THISTLE (SILYBUM MARIANUM L. GAERTN), AND LITTLE HOGWEED (PORTULACA OLERACEA L.) A COMPLETELY RANDOMAIZED DESIGN WITH FACTORIAL ARRANGEMENT OF TREATMENTS WAS CARRIED OUT WITH FOUR REPLICATIONS IN WEED LIBRARY RESEARCH, UNIVERSITY OF TEHRAN, IN 2008. FACTORES INCLUDED KIND EXTRACTS AT TWO LEVELS (ROOT AND SHOOT) AND DIFFERENT CONCENTRATIONS OF RYE AT SIX LEVELS (0, 6.25, 12.5, 50 AND 100). SEEDLING FRESH WEIGHT, LENGTH OF RADICLE AND COLEOPTILE AND PERCENTAGE OF GERMINATION, WERE MEASURED. RESULTS SHOWED THAT LOW CONCENTRATIONS HAVE POSITIVE EFFECT ON STUDIED TRAITS AND THE EFFECT OF ROOT EXTRACTS WERE MORE THAN SHOOT EXRTRACTS. SHOOT AQUEOUS EXTRACTS OF RYE IN COMPARISON ROOT EXTRACTS SHOWED THE MORE NEGATIVE EFFECTS IN ALL STUDIED TRAITS BECAUSE THAY HAVE MORE INHIBITORS.