Two studies are reported. Each was double-blind in which Spiramycin was compared to Erythromycin and a placebo, to determine the value of Spiramycin as a therapeutic agent in the control of periodontal disease. In Study 1, 48 adults with varying degrees of periodontal disease were randomly assigned to treatment and control groups. Assessments of gingival index, plaque height, pocket depth, crevicular fluid volume and wet plaque weight were made. During this 4-week clinical trial, the patients maintained their usual oral hygiene. The medication was administered systemically for 5 days, starting at the conclusion of week 2. Spiramycin significantly reduced the scores for the five parameters recorded. When comparison were made, the greatest recorded effect with Spiramycin treatment was found in patients with advanced periodontal disease. The indication of this trend favouring Spiramycin led to an extension of this clinical trial involving only patients with advanced periodontal lesions. This second study comprised 54 adults. The same parameters were measured over the same time period as in Study 1. Spiramycin again was responsible for the greatest reduction in the recorded scores. For example, average pocket depth was decreased by approximately 30%, whereas Erythromycin produced a reduction of 15%. It would appear that Spiramycin is of definite benefit in the management of periodontal disease, especially in the more advanced cases.