Cephaloridine was administered to 23 patients with early infectious syphilis, and observed for a minimum of 12 months after treatment. Clinical, darkfield, and serological results have been excellent with no observed allergic reactions or untoward effects. Included were five patients with known penicillin allergy. Two patients demonstrated Herxheimer's reaction. The results thus far are excellent but the drug still requires continued investigation over a longer period of time.