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Data on the geographical distribution of malaria and the genetic traits of thalas­semia and G-6-PD deficiency within the island population of Sardinia, Italy, are summarized. The traditional explanation for the genetic trait distribution, the re­sult of differential selection by endemic malaria, is called into question. Previous analyses had used altitude as an indirect measure of malaria; epidemiological information is presented to show that such an assumption is inadequate and incorrect. Utilizing morbidity data from an island-wide malaria survey conducted by Fermi, the present analysis does not replicate the expected correlation between malaria morbidity and gene traits, thalassemia and G-6-PD deficiency. An alternative hypothesis, that gene flow due to historical migrations during the Carthaginian and Roman epochs helps to explain the geographical distribution of thalassemia and G-6-PD deficiency, is offered.