For the purpose of developing controlled delivery devices for periodontal therapy which would release over several days, six fiber types made of tetracycline-loaded biocompatible polymers were manufactured and tested. Polyethylene, polypropylene, polycaprolactone, polyurethane and cellulose acetate propionate all released their drug load within 1 day. Ethylene vinyl acetate fibers, however, provided in vitro sustained release for periods up to 9 days. A bioassay was designed to measure levels of tetracycline achieved by local delivery which used growth inhibition of Bacillus cereus as a measure of the amount of tetracycline in measured volumes of gingival sulcus fluid on filter paper strips. By this assay, fibers made from 25% loaded ethylene vinyl acetate established initial concentrations of approximately 500 micrograms/ml. The measurement of tetracycline concentration resulting from the placement of these fibers into deep periodontal pockets as a packing material provided indication that concentrations of greater than 50 micrograms/ml could be maintained for months by weekly to monthly replacement. These studies indicate that monolithic fibers made of tetracycline-loaded ethylene vinyl acetate have characteristics which could prove useful as the basis of a tetracycline delivery system for the treatment of periodontal disease.