The in vitro study of the amoxicillin-clavulanate association has been carried out using a triple layer technique by means of paper strips which show a T configuration. Synergy observation proves to be most favorable with the following reservoir load: (a) when the latter is sufficiently low so that the inhibiting effect of the clavulanate and amoxicillin, taken in isolation, becomes weak or nil; (b) when the ratio between the two substances is amoxicillin 5, clavulanate 1. Under such conditions, the inhibition of the bacterial growth occurs solely in the confluence area of the substances. The neutralization of amoxicillin through penicillinase respectively after 4, 6 and 24 h of incubation makes possible an appraisal of the bactericidal action of the association.