The aim of this study was to assess on a large series of soccer players our previous reports on blood rheology and exercise performance. In 99 soccer players (Age 24,17 ± 0,42 yr; weight 75,87 ± 0,89 kg; VO2max 46,86 ± 0,95 mL/min/kg) an exercise test was performed for measuring maximal aerobic capacity and we measured blood viscosity at high shear rate (MT90 viscometer) and RBC aggregation (Myrenne MK1). The French questionnaire developped by the consensus group on overtraining of the French Society of Sports Medicine (SFMS) was also employed. The only hemorheologic statistical determinant of VO2max was hematocrit (Hct r = -0.2439; p = 0.0303). The lactate threshold 2 mmol/l was negatively correlated to M1 (r = -0.43224; p = 0.00847). There was a borderline correlation between the overtraining score at the questionnaire of the SFMS and plasma viscosity (r = 0.3080; p = 0.0532). Therefore, our study confirms that aerobic capacity in this sport is negatively correlated to hematocrit, that RBC aggregation is positively associated with blood lactate accumulation in blood during exercise, and that plasma viscosity is one of the parameters that increase when the athlete is on the edge of the overtraining syndrome. These data are consistent with previous reports about soccer players but caution is needed to extrapolate to other sports.