The effect of ketoprofen, an antiprostaglandin substance that inhibits the enzyme ciclooxigenase, on the mean pulmonary arterial pressure (mPAP) was evaluated in 10, male Jersey calves, of 1-2 months of age. Calves were born at sea level and exposed during 3 days to an environmental hypoxia of 3,320 m of high altitude. A group of 5 animals received destiled water as placebo (Control group), and other group received ketoprofen in dose of 3 mg/kg body weight for 5 consecutive days while at sea level (Treated group). The mPAP was measured by cardiac cateterism at sea level and 3 days after arriving to the high altitude. The mean values of mPAP (mm Hg) at sea level were: Control group 19.00 ± 0.94 and Treated group 21.00 ± 3.39; whereas at the high altitude were: Control group 39.50 ± 6.00 and Treated group 31.25 ± 5.70, and without significant differences. When data of the two groups were joined and analysed together, the values for mPAP at sea level (20.00 ± 2.68) were statistically different (p<0.05) from those at day 3 of exposition to high altitude (35.28 ± 7.16). The results suggested that ketoprofen had not effect on mPAP in Jersey calves exposed during 3 days at high altitude hypoxia.