Portal hypertension is a major consequence of any chronic liver disease and it represents the main mechanism of complication occurrence. Therefore, the assessment of portal hypertension presence is one of the most important steps in the management of any chronic liver diseases. The most accurate tool for portal pressure assessment is hepatic venous pressure gradient (HVPG) measurement, which has diagnostic and prognostic relevance. In this paper we review the methodology of HVPG measuring, together with the clinical relevance of this technique. Portal hypertension is defined as a HVPG higher than 5 mmHg, but clinically significant portal hypertension that predisposes to clinical decompensation is defined as HVPG higher than 10 mmHg. HVPG is useful for portal hypertension treatment monitoring. A decrease in HVPG greater than 20% or under the threshold of 12 mmHg is considered to be protective against portal hypertension-related events. Even if HVPG measurement is a safe procedure, it is still considered an invasive technique and not widely available. Therefore, non-invasive markers of portal hypertension were searched for. Until now only liver stiffness measurement by transient elastography has proved to be sufficiently accurate but there is still heterogeneity among the cut-off values for portal hypertension diagnosis.