Many new antibiotics and countless formulations of old ones have been introduced during the past three decades. None has supplanted BPG. It remains the only drug that can provide antibiotic blood levels for several weeks following a single intramuscular injection. This property makes BPG the ideal preparation for treponematoses and group A streptococcal infections in patients who are not allergic to penicillin and for whom single-session therapy is desirable or necessary. Sensitivity reactions from BPG are less frequent and less severe than those from aqueous or procaine penicillin G. In certain situations, such as the prevention of rheumatic fever and rheumatic heart disease, the fear of a reaction in a patient with a negative past history of penicillin allergy is no justification for withholding BPG when it is clearly the drug of choice.