In the Fall of 1932 the Public Health Service initiated a study1 of untreated syphilis in the male Negro in Macon County, Ala. The original group of participants included approximately 400 syphilitic patients and 200 nonsyphilitic controls. A few of the patients had clinical manifestations of late syphilis, but in the great majority the diagnosis was based on history of a primary lesion and two or more reactive serologic tests for syphilis. The tests employed were the Kolmer complement fixation and the Kahn standard flocculation, performed at the National Institute of Health.
In January, 1958, or 25 years after initiation of the study, 209 of the surviving participants were located and examined. Blood specimens were divided, one sample being sent to the Venereal Disease Research Laboratory at Chamblee, Ga., the other to the Venereal Disease Experimental Laboratory at Chapel Hill, N.C. Between the two laboratories, a complete battery of