This study examined the effects of psychological stress on hemoconcentration in women. Hematologic and hemodynamic variables were assessed in 17 women before and after a 3-min speech task. Significant changes in hematocrit, hemoglobin levels, red and white blood cell (WBC) count, and calculated plasma volume occurred during psychological stress (all ps < .05). Significant increases were also observed for total cholesterol, triglycerides, high density lipoprotein cholesterol, low density lipoprotein cholesterol, and free fatty acid (FFA; all ps < .05) during stress. After statistically correcting for the hemoconcentration effects of decreased plasma volume during stress, only WBC count and FFA concentration remained significantly elevated during the stress task (p < .006 and p < .05, respectively). In sum, acute stress alters hemoconcentration in women, which in turn can account for most stress-induced changes in lipids.