This preparation is available in the form of a sterile dry powder containing benzylpenicillin potassium (or sodium) and procaine penicillin with a suitable amount of suspending and buffering agents. The advantage of such a preparation is that it can exert both prompt actions due to the high initial blood levels produced by the soluble potassium salt, and the prolonged action of the insoluble procaine penicillin salt which is adsorbed and excreted slowly. Therefore, a single dose injection of this preparation can maintain an effective concentration in blood for 12-24 hours.