The A. presents the results of preliminary studies on sicklemia. The methods recommended to put sicklemia into evidence are: a) Carbon dioxide (Hahn & Gillespie's method) when an immediate result is desired; b) Beck & Hertz's for experimental studies (sicklization phenomenon); c) Emmel's for producing evidence on a large scale. It is a practical method allowing the use of coagulated blood or of blood containing anticoagulative substances if isotonicity maintained. Agglutination of red blood corpuscles by the sera anti-A and anti-B does not check sicklization: thus, with a single preparation two tests are practicable: determination of blood group, and sicklemia; d) maceration of tissues preserved in formol or absolute alcohol. The best results are obtained by macerating spleen, liver, lung, kidney or pancreas. Use has been made of material preserved for even 26 years. By means of this method it becomes possible to draw up a retrospective index of sicklemic individuals and its appliance to anthropologic and etnographic studies. The index of sicklemic individuals met with, was of 10%, on examining a heterogeneous grouping of 1130 negroids or cross-breeds of this etnia, thus distributed: Negroids ..... 890 10.4%, Cross-breeds of negroids and caucasoids (mulattoes) ..... 140 8.0%, Cross-breads of negroids, caucasoids ande mongoloids..... 100 9.0%. The investigation was negative in 30 mongoloid and 100 caucasoid individuals. in 58 sicklemic individuals, carriers of morbid conditions producing circulatory stasis, no anatomicopathological, changes of sickle cell anemia was observed. These findings contradict the hypothesis that stasis is a sufficient factor for the transition from a sicklemic to an anemic condition. In 8 cases of infection by P. falciparum, 2 cases by P. falciparum and P. vivax and 3 cases by P. vivax in sicklemic individuals no symptom of sickle-cell anemia was observed. It was verified that parasitism...