This study was conducted to determine the most suitable irrigation frequency and quantity in cucumber grown under field conditions. The amount of water used was based on pan evaporation from a screened Class-A pan. Irrigation treatments consisted of two irrigation intervals (I1: 4 and I2: 8 day), and three plant-pan coefficients (Kcp1: 0.50; Kcp2: 0.75 and Kcp3: 1.00). Plants were first watered at the transplanting date and scheduled irrigations were initiated after 4- and 8-day intervals. Irrigation quantities applied to the treatments varied from 320 to 509 mm; seasonal plant water comsumption or evapotranspiration of irrigation treatments varied from 391 to 597 mm; and the cuccumber yield varied from 17.99 to 45.20 ton ha -1. The highest total yield was obtained from I2Kcp3 treatment. Moreover, Kcp3 treatments had the highest early yield. Et/Epan ratio according to treatments ranged from 0.29 to 1.25. Irrigation treatments had significant effects (P < 0.01) on yield and there were significant positive linear relations (P < 0.01) between the fruit number and irrigation water and between the plant water compsumption and the yield. In conclusion, Kcp3 treatment with 8-day-irrigation interval is recommended for cucumber grown under field conditions in order to get higher cucumber yield and to save time and labor. Furthermore, the Et/E pan equation of the best irrigation treatment (I2Kcp3) of this study (Et = 1.05Epan + 96.72) should, therefore, be used in the scheduling irrigation programs in similar conditions. © 2005 Elsevier B.V. All rights reserved.