Abstract: Controlled delivery of biologically active agents such as pharmaceuticals to body sites is accomplished by combination with a monoglyceride and a vegetable oil. Upon contact with an aqueous liquid, the composition forms a reverse hexagonal liquid crystalline phase matrix which releases the active agent in controlled fashion. The method of delivery is particularly useful for the treatment of periodontal disease by insertion of the liquid crystalline phase precursor composition directly into the periodontal pocket, where water from the gingival fluid induces the spontaneous in situ formation of the reverse hexagonal liquid crystalline phase matrix.