Eighty patients, having received periodontal therapy previously, were divided into four groups, corresponding to one of four different types of dental floss being used. Seven to ten days after receiving a thorough prophylaxis, each patient had oral hygiene instruction by video tape, was given a toothbrush and a quantity of the test floss. At 0, 28 and 56 day intervals, the patients were scored for crevicular fluid flow and gingival bleeding. Data were analyzed statistically. Johnson and Johnson unwaxed dental floss was found to be slightly less effective in reducing gingival bleeding at the 56th day. It was also found that crevicular fluid flow was least with waxed floss use at the 56 day session. However, the range of variations was so minimal that no clinical significance could be ascribed to either finding. There were patients in each of the four floss groups with no fluid flow or bleeding during all three sessions.