Chronic exposure to hypoxia increases pulmonary artery pressure (PAP) in highlanders, but the criteria for diagnosis of high altitude pulmonary hypertension (HAPH) are debated. We assessed cardiac function and PAP in highlanders at 3250 m and explored HAPH-prevalence using different definitions.Central Asian highlanders free of overt cardio-respiratory disease, permanently living at 2500-3500 m compared to age-matched lowlanders living <800 m. Participants underwent echocardiography close to their altitude of residence (at 3250 m versus 760 m).173 participants (97 highlanders, 76 lowlanders), mean±sd age 49±9 years (49% females) completed the study. Results in lowlanders versus highlanders were: systolic PAP (23±5 versus 30±10 mmHg), right ventricular fractional area change (42±6 versus 39±8%), tricuspid annular plane systolic excursion (2.1±0.3 versus 2.0±0.3 cm), right atrial volume index (20±6 versus 23±8 mL·m-2), left ventricular ejection fraction (62±4 versus 57±5%) and stroke volume (64±10 versus 57±11 mL), all between group comparisons p<0.05. Depending on criteria, HAPH-prevalence varied between 6 and 35%.Chronic exposure to hypoxia in highlanders is associated with higher PAP and slight alterations in right and left heart function compared to lowlanders. The prevalence of HAPH in this large highlander-cohort varies between 6% according to expert consensus definition of chronic high-altitude disease to 35% according to the most recent PH-definition proposed for lowlanders.