After a search of the literature including computerized data bases on the economic potential of various plants, experiments designed to improve the extraction of silica from the horsetailEquisetum arvense L. were carried out. Improved yields of colloidal silica were obtained by sonication in a shorter time than by conventional extraction with boiling distilled water. However we conclude that commercial exploitation of silica (colloidal or solid) fromEquisetum arvense is not feasible at present because: growing conditions of this plant species are not yet well defined; the disappearance of the plant during the winter months limits its period of exploitation; the silica content of the plant can vary over a six-fold range depending on weather and soil conditions, and so its economic potential is unpredictable.