Modern jet fighter aircraft are capable of achieving G acceleration profiles that subject pilots to extremely high inertial forces in the head-to-foot direction (+Gz). Severe physical stress is imposed by the environment of rapid-onset, highly-sustained +Gz. Despite the importance of monitoring pathophysiological alterations related to +Gz exposure, there have been only a few studies concerning the physical status of human centrifuge trainees. To investigate alterations in serum biochemical and complete blood count parameters occurring in subjects exposed to high +Gz. Eighteen jet fighter pilots were exposed to +9Gz on a human centrifuge. Blood samples were obtained before and immediately after the centrifugation. Serum biochemical and hematological analyses were performed. The total protein level increased from a mean of 7.53±0.07 g/dL to 7.91±0.09 g/dL, a significant 5.0% (p<0.001) increase. The white blood cell, red blood cell and platelet counts also increased from a mean of 6.72±0.23 k/μL, 5.06±0.06 k/μL and 230.00±12.98 k/μL to 9.02±0.50 k/μL, 5.25±0.08 k/μL and 247.11±13.73 k/μL, respectively; significant elevations of 34.2% (p<0.001), 3.8% (p<0.001) and 7.3% (p=0.004), respectively. In addition, hemoglobin (2.0%, p=0.036) and hematocrit (4.3%, p<0.001) increased significantly after the centrifugation. We demonstrated that the serum levels of total protein and complete blood count parameters are significantly elevated during high +Gz exposure. Our data raise the possibility that intense muscular exertion during anti-G straining maneuver could be one of the causes of post-centrifuge hemoconcentration.