The material for this study includes a survey of 2,439 patients with syphilis, of whom 913 had early infections in the primary or secondary stage. In this series, 56 patients were discovered who presented various forms of cutaneous and mucosal relapse. These have been considered and reported on separately.1 In the series were also 4 cases of possible reinfection, 2 from departmental and 2 from private records, and 2 additional private cases which illustrate certain problems that arise in the attempt to differentiate clinically between what Balzer,2 Hecht,3 Bernard4 and, recently Lortat-Jacob, Roberti and Poumeau-Delille5 called pseudoreinfection and true reinfection. As pseudoreinfection is essentially relapse, we were impressed with the differential significance of this problem, and from a review of the literature, our study of relapse and the 6 illustrative cases mentioned offer a critique of the problem of clinical differentiation of reinfection from the