A review of the literature on sickle cell trait was completed by Sears in 1978. Since that time, several papers have been published concerning the possible health risks of sickle cell trait. Data presented from these studies show that there is no association with sickle cell trait and overall survival, overall mortality, overall morbidity, frequency and length of hospitalization, short-term survival of renal transplant recipient, and inheritance of glucose-6-phosphate dehydrogenase. Association with sickle cell trait is very likely in the following: splenic infarction at high altitudes (over 10,000 feet), in unpressurized airplane flight and mountain climbing, bacteriuria and pyelonephritis in pregnancy, hyposthenuria, hematuria, and delayed resolution of anterior chamber hyphema. Although these conditions have a statistical significant association with sickle cell trait, they occur quite infrequently. Thus, when they are observed, other causes should be sought before attributing them to sickle cell trait. Reduced mortality from Plasmodium falciparum infection also shows significant association with sickle cell trait.