Rossi-Espagnet, A., K. W. Newell, R. MacLennan, J. B. Mathison (Division of Epidemiology, Tulane University, New Orleans, La.) and S. P. H. Mandel (Department of Community Medidne, University of Vermont, Burlington, Ve.). The relationship of sickle cell trait to variations in blood pressure. Amer. J. Epid., 1968, 88: 33 44.—The investigation that forms the object of this paper is related to the known fact that Negroes exhibit higher blood pressures and higher and earlier mortality due to hypertensive heart disease and cerebrovascular accidents than non-Negroes. The hypothesis of a possible association between sickle cell trait and variations of blood pressure was tested in two Negro populations of Colombia, South America in an attempt to find a possible explanation for the differences mentioned above. The sickle cell trait is widely distributed in the Negro race and relatively uncommon among non-Negroes, and certain types of renal damage have been found to be associated with this. A total of 2, 155 persons of both sexes aged 20 years or more were examined in defined sections of two Columbian towns at sea level and at 1, 000 m of altitude, respectively. Blood pressure values were obtained by single casual measurements using mercury manometers. The results of the study indicated that there were no significant differences in either systolic or diastolic blood pressures of Negroes who had positive sickle cell slide tests as compared with Negroes who had negative sickle cell slide tests.