The material presented in this paper represents a careful clinico-pathological study of the 54 cases of thyroid malignancy which have been reported by the pathological laboratory of the New York Hospital during the past thirteen years, supplementing a previous report (9). During this period a total of approximately 100,000 admissions to the hospital have been made. Of this number, slightly over 28,000 have had surgical specimens diagnosed pathologically. Among these 28,000 surgical specimens, some 1,600 have been thyroid glands; 855 of which have represented thyroid tumors, an incidence of a little more than 50 per cent. In this group of tumors 42 have been histologically and clinically malignant and are included in this report. The other 12 cases have come from outside sources, chiefly through the kindness of Dr. John Rogers, to whom we are indebted both for the material and for the clinical histories. One case, of particular interest as representing an intermediate phase between adenoma and subsequent pseudo-sarcomatous malignant degeneration, was sent us through Dr. John Scott of Louisville, Kentucky. Analyzing these figures, we see that the incidence of thyroid malignancy in the New York Hospital series represents almost exactly 2.5 per cent of all thyroid specimens, and about 4.7 per cent of all thyroid tumors. These percentages are quite comparable to those of other observers. In 1929, one of us (LWS) reported another series of 67 cases of thyroid malignancy from the Lahey Clinic, in which the incidence was 1.68 per cent. In the Mayo Clinic, the figure runs about the same: 1.6 per cent of all thyroid specimens from 1910 to 1916. Graham in Cleveland reports a similar figure, as do Craver (4) and Haagensen (7) from the Memorial Hospital in New York.