Open pitaya (Stenocereus thurberi) flowers were marked at 10, 20, 30 and 40 days after floration (DAF). When fruit were formed, they were collected from each of the dates with the objective of evaluating physical, physiological and quality changes before and after harvest. In fruits with different DAF, the analyses of fruit size (diameter and length), weight, density, firmness, color in pulp and peel (L*, a* and b*), respiration rate (CO₂) and ethylene production were carried out. In the case of ripe and overripe fruit, in addition to the variables mentioned above, pH, percentage of total soluble solids TSS and total acidity (% citric acid equivalents) were evaluated. Fruit with 40 DAF were stored for up to 14 days at 25 ℃ and 80% RH to evaluate daily changes in respiration rate and ethylene production. It was found that during development the fruit tended to grow more in length than in diameter. In color, the best indicators of changes during fruit development were the parameters L* and b* for peel and for flesh L* and a*. For firmness in pitaya fruits, no significant differences were found with the methodology used. Changes in ethylene production and respiration rate during storage and development showed the usual behavior of climacteric fruits. Pitaya fruits with 40 FDD presented quality characteristics similar to those accepted by the consumer for this type of fruit. It is concluded that it is possible to evaluate the different stages of development in DDF of pitaya fruit based on the changes of the color space variables L*, a* and b*, in addition to the fact that the fruit follows the classical climacteric behavior.