Lymphocytary subpopulations have been determined, by means of monoclonal antibodies, in 24 patients afflicted with iron deficient anaemia, repeating the determination in 15 of the patients after an adequate iron therapy. In iron deficient patients a significant reduction of the percentage of lymphocytes T (OKT3+) has been observed, in comparison with normal controls, as well as a significant reduction of the percentage of cells OKT8+, with a significant increase of the OKT4+/OKT8+ ratio. In the 10 patients who at the moment of the revaluation did not present any longer either anaemia or iron deficiency, the percentage of lymphocytes OKT3+ and OKT8+ had returned to normal values, as well as the OKT4+/OKT8+ ratio. The 5 patients still resulting anaemic in course of control presented, on the contrary, a significant reduction of cells OKT3+ and OKT8+, while the OKT4+/OKT8+ ratio resulted lightly increased, however not significantly.