Since the wide-range orally administered antibiotics, aureomycin (Finland and others, 1948) and terramycin (Willcox, 1951; Willcox and Findlay, 1952), were first reported as effective in nongonococcal urethritis the question has arisen of their relative efficacy. In a previous paper a comparison was made of the relative efficacy of terramycin, aureomycin, chloramphenicol, sulphonamides, streptomycin, and penicillin in non-gonococcal urethritis (Willcox, 1953). In assessing the failures no attempt was made to distinguish between relapse and re-infection, except that all such occurrences noted after a symptom-free period of 3 months were assumed to be re-infections. This period was commonly accepted as an adequate criterion of cure of non-gonococcal urethritis when the disease was treatedroutinely with sulphonamides. As any extension of this interval after treatment with the antibiotics is concerned more with the possibility of masked syphilis than with uncured urethritis it is considered that this arrangement is reasonable and fair. The results of this previous study are shown in Table I.