24 healthy volunteers abstained from tooth-cleaning for 17 days. Parameters of gingival health were recorded on days 1 and 17. On days 4, 6, 8, 11, 13 and 15, each volunteer randomly received, on a double-blind basis, 100 ml of 10 mM flurbiprofen solution in buffered preservative to one upper quadrant of the mouth. The contralateral quadrant received preservative only. Applications were made using a pulsed jet irrigating system. Gingivitis developed in all patients and there were no significant differences between the treatments for gingival index or pocket probing depths. When gingival health was re-established, 4 volunteers had a further 3 irrigations of flurbiprofen at intervals of 2 days. Plasma levels of flurbiprofen were determined after the 1st and 3rd irrigations. Assays showed that the drug was present in the plasma of all 4 subjects (range 0.2-0.7 micrograms/ml). Gingival health was re-established in 6 further volunteers from the original study. They then abstained from toothbrushing for 17 days, during which one maxillary quadrant was irrigated with the buffered preservative solution. The irrigations were made on the same basis as in the original study. Gingivitis again developed in these quadrants, although when the results were compared to the equivalent data from the first investigation, significantly greater median values for probing pocket depths and gingival indices were found in the latter study. Therefore, it appears that systemic absorption of flurbiprofen may have reduced the severity of the developing inflammatory lesions.