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Pitaya (Stenocereus sp.) is a fruit native to arid and semiarid areas of Mexico. It has high antioxidant activity mainly due to its contents of betalains and phenolics, but its consumption is limited due to very short shelf-life and not very recognized flavor. A beverage of pitaya and pineapple was formulated to improve sensory properties. A high hydrostatic pressure (HHP) study at 400-600 MPa and 25 A degrees C for 2-10 min was applied in the beverage and the effect on the contents of vitamin C, total phenolics and betalains, and the pectin methylesterase (PME) activity of pitaya-pineapple beverages, was evaluated. The effect of the come up time (CUT) was also studied. Vitamin C contents increased from 5% at 600 MPa-CUT to 64% at 400 MPa/CUT. Total phenolic concentrations decreased (20-48%) at all processing conditions tested at 400 MPa/CUT, total betacyanins were retained. At 500 MPa/10 min losses of betaxanthins of up to 6% occurred. The maximum PME activity decrease was 23% at 600 MPa 5 min, but an increase of PME activity 7% was observed at 400 MPa/10 min. HHP seem to be a good option to retain most of the antioxidant compounds in pitaya-pineapple beverage, but more studies are necessary to inactivate PME.