The Poaceae family has been reported in several published works to show evidence of allelopathic activity. Secondary metabolites as phenolic compounds, hydroxamic acids, flavonoids, etc. commonly occur in both cultivated and wild Gramineae. This article, therefore, attempts to review and synthesize past and recent findings concerning the allelopathic activity of this family. It reviews the type of the activity (stimulative or inhibitive), the donor plant, the target species, and the mode of action in each case.