Since in the literature basophilia is frequently related to myxedema, we evaluated basophilic leukocytes in patients with hypothyroidism, applying routine techniques used in clinical laboratories. The study included normal persons, untreated patients with hypothyroidism, and euthyroid subjects with hyperlipidemia. The number of circulating basophils was determined by differential counts of Pappenheim stained blood smears. No difference in relative and total basophil counts was detected in patients with hypothyroidism as compared to healthy controls (1.0% and 58.1 basophils/microliters vs. 0.8% and 50.8 basophils/microliters, respectively). The percentage of basophils in myxedema associated with hypercholesterolemia amounted to 1.0%, their absolute number to 57.6/microliters; in hypothyroid patients presenting normal serum cholesterol levels, the relative and absolute numbers of basophilic leukocytes was not statistically different (0.83% and 61.1 basophils/microliters, respectively). We conclude that in patients with hypothyroidism the number of basophils is not statistically different from the values of basophils in healthy controls. Furthermore, the number of peripheral blood basophils in hypothyroidism is not related to the serum cholesterol level.