CONFLICT OF INTEREST: NONE DECLARED Introduction The collection of platelets by apheresis is considered as a very great progress in transfusion medicine. A larger yield (total number of collected platelets) is obtained if the donor has a greater number of initial platelets and if the separation is done in a shorter time. One of the parameters is also the efficiency of the platelet collection (expressed in percentage) on the value of which different factors may have direct or indirect influence. Aims To calculate the efficiency of platelet collection with the separator Fenval Baxter AMICUS and to compare the efficiency of platelet collection with this separator in relation to the initial value of donor hematocrit. Donors and Methods The donors who participated in this study were divided into groups according to the value of the donor’s ‘hematocrit before separation. Group C consisted of donors whose initial value of the hematocrit was lower or equal to 46%. Group D consisted of donors whose initial value of the hematocrit was higher than 46%. The process was carried out on Fenval Baxter AMICUS. The expected efficiency of the collection was obtained by dividing the total number of collected cells by the expected total number of processed cells, i.e. the total number of cells passed through the equipment. Results In the 258 separations which satisfied the fixed criteria were men in 226 cases (87.6%) and women in 32 (12.4%). There is a statically significant difference in the platelet value between the groups and this value is higher in group D than in group C. The average value of platelets before separation was 46.66. The range of minimal and maximal value is from 38.8 to 52.4 ±2.78. The initial value of hematocrits of the donor does not intervene in the length of the separation, but it has a significant effect on the efficiency of the platelet collection. Increases in the number of hematocrits significantly decrease the efficiency of platelet collection. In practice it means that we can base on this fact make a better selection of donors. In this kind selection, one should prefer a donor with a higher number of initial platelets and lower levels of hematocrits. In that way we can collect a more important yield, have a shorter length of separation and increase the efficiency of platelet collection. Its advantage is as well medical because of a more important yield but also financial because of the decrease of the length of the separation and the increase in efficiency. Key words: value of hematocrits, donors, apheresis, platelets, efficiency.