The aim of this research was to determine the amount of irrigation water, irrigation interval, and water consumption that gave the greatest yield, to determine the effect of irrigation on fruit quality characteristics, and to investigate variations in soil moisture in Redhaven peaches irrigated by drip irrigation in the Aegean region of Turkey. The study was performed in 2003 and 2004 on split plots in randomized blocks with three replications. Main treatments were 3 and 6 days between irrigations, and subtreatments comprised four different pan coefficients (K-p1.25, K-p1.00, K-p0.75, and K-p0.50). According to the 2-year averages of peach yields, the effect on yield of the amount of irrigation water was found to be significant (p < 0.01), but the effect of the irrigation interval was found not to be significant. Total yield varied between 5,966 and 16,340 kg ha(-1), and marketable yield between 5,349 and 14,164 kg ha(-1), according to irrigation treatments. A maximum average yield of 14,101 kg ha(-1) was obtained from treatment K-p1.00. Average irrigation water amount for this treatment was 482 mm, average water consumption was 705 mm, and the K-pc value was 0.785. Maximum water-use efficiency (WUE) of 2.02 kg m(-3) was obtained from K-p1.00. The yield response factor (ky) was found to be 1.2. Weight of individual fruit varied between 203 and 253 g, height varied from 6.3-6.6 cm, diameter from 7.2-7.7 cm, soluble dry matter from 10.8-14.5%, and juice pH from 4.14-4.37. In the years of the study, the declining trend of soil moisture was greater in the treatments that received little irrigation water than in those that received more. After irrigation was ended, soil moisture decreased rapidly and eventually reached the wilting point. To conclude, when setting up a drip-irrigation program for fully grown peach trees in the Aegean region, the irrigation interval may be 3 or 6 days. The amount of water to be applied at each irrigation can be determined by correcting the total evaporation from a Class-A evaporation pan over the chosen irrigation interval by a coefficient of 0.785. DOI: 10.1061/(ASCE)IR.1943-4774.0000310. (C) 2011 American Society of Civil Engineers.