Chronic Heart Failure (CHF) is accompanied by a whole range of symptoms, which significantly decrease the quality of life; these typically concern dyspnoea, fatigue and exercise intolerance. The objectification of the patients condition but must have an effective means of evaluation. One such resource is cardiopolmonary exercise (CPX) testing with it is functional parameters. CPX test with its functional parameters is one of such means. VO2peak is undoubtebly the parameter, which was used the most often in the past 25 years, however, it has many limitations. It is reason, why the evaluation of ventilation effectiveness using the VE/VCO2 slope is becoming more and more the centre of Czech and foreign interest of cardiologists abroad. Foreign studies have unambiguously proven that because of the absence of the fundamental limitations, such as in case of VO2peak, the VE/VCO2 slope is a stronger predictor of the amount of hospitalizations and of mortality in the population of patients suffering from CHF. This short overview intends to inform of the significant merit of this parameter. That is the reason why the VE/VCO2 should be classified as a standard criterion in indication of heart transplantations, but also in evaluation of seriousness and prognosis in population of patient suffering from HF.Key words: heart failure - mortality - prognosis - ventilation efficiency - VE/VCO2 slope.