By the analysis of our previous studies, functional and biochemical markers related to ETS exposure are discussed. 18 healthy never smokers, 12 men (67%), 6 women (33%), 21 to 55 years old (mean:34+/-9 ys.) underwent twice - in a smoking free environment and in the same environment polluted by 35 ppm carbon monoxide from cigarette smoking- brachial artery ultrasonography, exercise stress testing, heart rate (HR) and blood pressure (BP) monitoring, carboxyhemoglobin (COHb) dosage. In ETS exposure compared with no exposure, flow-mediated dilation mean value (FMD), assessed by ultrasonography, was 6.8+/-7.8% versus 12.6+/- 7.8%, significantly impaired; mean HR was 89+-4 beats/minute-for 2h duration- versus 77+/-4 beats/minute; systolic BP was 134+/-17 mmHg versus 124+/-21 mmHg; diastolic BP was 79+/-4 mmHg vs 76+/-5 mmHg, with no change. Bicycle exercise stress testing showed a significantly increase in mean time to recovery baseline parameters, 19.04+/-4 minutes versus 8.5 +/-4 minutes (P less than 0.01),and mean COHb was 1.7+/-0.4% vs 0.8+/- 0.4 (P less than 0.01). From the results observed, five markers of ETS exposure could be identified and, then, discussed:1. Impaired FMD, effect of endothelial dysfunction, 2. Transient increase in systolic BP; 3. HR increase; 4.Diminished tolerance to exercise; 5. Increased COHb blood concentrations.