The present study assesses the impact of "sports anemia" on screening tests performed on participants in an endurance-training program. Medical charts of 48 naval Special Forces trainees and 48 submarine trainees were reviewed. We compared the results of red blood cell count, hemoglobin concentration, hematocrit (Hct), and mean corpuscular volume performed at recruitment and after 2 years. No differences were noted between baseline values. The Hct and red blood cell count decreased significantly in the Special Forces trainees after 2 years of training (p = 0.002 and p = 0.05, respectively), remaining unchanged in the submariners. Hct decreased by 2 ± 4.14%, whereas red blood cell count decreased by 0.13 ± 0.44 M/μL. A reduction in Hct may be expected in Special Forces trainees engaged in long-term endurance training. Because these lower values were not seen in an otherwise identical group of submarine trainees, they could be attributed to the endurance training.