Abstract. Sport practicing, due to the special conditions under which it occurs, needs an immune system which could assure a perfect health status. The immune system has two components: the innate immune system (IIS) and the adaptive immune system (AIS). The number of lymphocytes per mm (normal = 2500 – 3500) may represent a useful marker for the diagnosis of the protein-calorie malnutrition.
Specialists in hematology recommend the calculation of the leukocytes/lymphocytes coefficient (threshold value = 0.35).
The total lymphocyte number may represent a marker of malnutrition only if we exclude an infection, a disease associated with the depression of the immune system (but the high-performance sports do not depress the immune system?) or a hematological disease; stress and corticotherapy, often used by athletes, may also induce immunodepression! It has followed the evolution of the coefficient leukocytes/leukocytes in various steps of our study carried out during a sportive year, upon the volleyball players from the team ,,Timisoara University”.
Anyway, in the absence of other specific tests, the supervision of this coefficient could be used in the medical-sportive control of volleyball players, participants in internal or international competitions, with a guiding marker of the immune reactivity compared to the stress induced by the sportive effort.

Key words: immune system, leukocytes/lymphocytes coefficient, athletes.