Next to performing an expert physical examination, a blood sample submitted for a complete blood count is the most basic tool available to owners or veterinary practitioners. Reference values of complete blood count were determined at 6 different ages in 114 Thoroughbred foals during the second month of life. Hematologic results were as follows: RBC 8.2-10.5 ($10^6/{mu}l$), Hb 10.9-13.3 (g/dl), HCT 28.2-35.2 (%), MCV 30.7-35.8 (fL), MCH 11.9-13.5 (pg), MCHC 37.9-40.5 (g/dl), RDW 24.5-25.7 (%), PLT 146.3-256.4 ($10^3/{mu}l$), MPV 6.7-8.3(fL), total WBC 8.1-12.5 ($10^3/{mu}l$), basophils 0.0 ($10^3/{mu}l$), eosinophils 0.0-0.3 ($10^3/{mu}l$), neutrophils 2.4-8.6 ($10^3/{mu}l$), lymphocytes 1.8-2.9 ($10^3/{mu}l$) and monocytes 0.0-1.4 ($10^3/{mu}l$). The results of this study serve as reference ranges for Thoroughbred neonatal foals populations and can be useful for health control, regular examination and pre-sale soundness examination.