We investigated whether exposure to the 915 MHz radiofrequency identification (RFID) signal affected circulating blood cells in rats. Sprague-Dawley rats were exposed to RFID at a wholebody specific absorption rate of 2 W/kg for 8 h per day, 5 days per week, for 2 weeks. Complete blood counts were performed after RFID exposure, and the CD4 þ /CD8 þ ratio was determined by flow cytometry. The number of red blood cells (RBCs) and the values of hemoglobin, hematocrit, and RBC indices were increased in the RFID-exposed group compared with those in the cagecontrol and sham-exposed groups (P < 0.05). However, the RBCs and platelet numbers were within normal physiologic response ranges. The number of white blood cells, including lymphocytes, was decreased in RFID-exposed rats. However, there was no statistically significant difference between the sham-exposed and RFID-exposed groups in terms of T-cell counts or CD4 þ /CD8 þ ratio (P > 0.05). Although the number of circulating blood cells was significantly altered by RFID exposure at a whole-body specific absorption rate of 2 W/kg for 2 weeks, these changes do not necessarily indicate that RFID exposure is harmful, as they were within the normal physiological response range. Bioelectromagnetics. 39:68-76, 2018.