(1) The technic and the results of the local injection of penicillin in acute circumscribed areas of infection in over three hundred ambulatory patients are presented. (2) Experience with this method of local therapy with penicillin has demonstrated that it is safe, effective and economical. There were no complications. (3) Because of the impermeable inflammatory barrier surrounding an acute localized infection, penicillin, when given parenterally, may not reach a sufficient concentration in the affected area for therapeutic effectiveness. (4) By local injection it is possible to reach a concentration in the infected area far in excess of the highest levels obtained by intramuscular administration. (5) Following injection directly into the affected tissue, there is almost immediate improvement and recovery is established in a few days. (6) Extremely gratifying, in addition to the rapid healing time, is the cosmetic result obtained. There is practically no loss of skin and no deforming scars are seen as usually found following surgical intervention. (7) This procedure is not recommended for the treatment of the cellulitides, for infections in the dangerous areas of the face, or for bone felons. (8) Surgical judgment must be exercised in each individual case.