Penicillin is the first therapeutic agent in the history of medicine that is effective in the treatment of both gonorrhea and syphilis.1 However, the great difference in the apparently curative doses of penicillin in the treatment of these two diseases presents a grave potential problem in that early syphilis may be masked and delayed by the use of doses of penicillin which are curative for gonorrhea but which are totally inadequate for syphilis. That this problem may be real we wish to illustrate by the report of the following case. REPORT OF A CASE D. S., a 28 year old Negro, was referred to the department of dermatology of Northwestern University on May 3, 1944, because of a discrete papulopustular eruption of one month's duration. The patient gave the following history, which agreed in every detail with the official Navy records. In February 1944 he enlisted in the