The delivery of chlorhexidine by spray systems have been found useful in controlling plaque in handicapped individuals. This study using a single blind crossover design compared chlorhexidine delivery by mouthwash and spray for plaque inhibitory effects. A group of 14 volunteers participated in two 4 day, no oral hygiene regimens. During one regimen chlorhexidine was professionally sprayed onto the teeth twice a day and during the other chlorhexidine was rinsed twice a day under supervision. Plaque regrowth from a zero baseline was recorded using a plaque index and by area. Little plaque accumulated during the two periods. There was no significant difference in plaque measurements following the use of the spray or mouthwash. This study demonstrated that chlorhexidine when sprayed under optimal conditions was as effective as a mouthwash at controlling plaque despite only requiring one seventh of a dose from a rinse. The results have implications for the use and delivery of chlorhexidine for plaque control and are relevant to the proposed mode of action of this antiseptic.