Mental challenge (MC) applied during orthostatic challenge (OC) increases cardiovascular responses. Passive head up tilt (HUT) and mental arithmetic (MA) are laboratory-based models for providing OC and MC, respectively. We investigated whether MC applied before OC elicits synergergistic responses in orthostatic heart rate, heart rate variability and arterial blood pressure. 15 healthy young males were subjected to two randomized protocols: a) OC and b) MC before OC, with sessions randomized and >=2 weeks apart. Beat to beat continuous hemodynamic variables were measured and saliva samples taken for hormonal assay.OC alone increased heart rate from 59 ± 7 (baseline) to 80 ± 10 bpm (mean ±SD) and mean arterial blood pressure from 88 ± 10 to 91 ± 14 mmHg. MC applied before OC resulted in greater, but not significant, increases in heart rate and cardiac output. Mental challenge applied preceding HUT induced increases in orthostatic cardiovascular responses that are, however, not different from those compared with HUT alone. While central drive induced by mental challenge adds to physiologically mediated cardiovascular reflexes, beneficial effects of mental challenge on orthostatic cardiovascular responses are not present when mental challenge is applied before orthostatic challenge.