Almost a century ago Billroth1 described two patients in both of whom developed more than one primary malignant neoplasm. Although not published until 1869, one of these patients was reported in 1860 according to Warren and Gates2 and Judge.3 Since that time, there has been a permutation of the occurrence rate of this disease from that of a rare medical curiosity to a commonplace medical enigma today. Although Renaud4 in 1847 and Rokitansky5 in 1855 apparently reported the first patients with multiple primary malignant tumors, these are poorly documented and Billroth is usually credited with the first reports which stimulated interest in this phenomenon. Selection of Patients The patients of this study were derived from the Tumor Registry of the West Virginia University Medical Center between August 1960 and July 1967. The diagnosis of multiple primary malignant disease was determined by the criteria established by