The impact of the Dietary Approaches to Stop Hypertension (DASH) diet on kidney stone formation is unknown. We prospectively examined the relation between a DASH-style diet and incident kidney stones in the Health Professionals Follow-up Study (n = 45,821 men; 18 yr of follow-up), Nurses' Health Study I (n = 94,108 older women; 18 yr of follow-up), and Nurses' Health Study II (n = 101,837 younger women; 14 yr of follow-up). We constructed a DASH score based on eight components: high intake of fruits, vegetables, nuts and legumes, low-fat dairy products, and whole grains and low intake of sodium, sweetened beverages, and red and processed meats. We used Cox hazards regression to adjust for factors that included age, BMI, and fluid intake. Over a combined 50 yr of follow-up, we documented 5645 incident kidney stones. Participants with higher DASH scores had higher intakes of calcium, potassium, magnesium, oxalate, and vitamin C and had lower intakes of sodium. For participants in the highest compared with the lowest quintile of DASH score, the multivariate relative risks for kidney stones were 0.55 (95% CI, 0.46 to 0.65) for men, 0.58 (95% CI, 0.49 to 0.68) for older women, and 0.60 (95% CI, 0.52 to 0.70) for younger women. Higher DASH scores were associated with reduced risk even in participants with lower calcium intake. Exclusion of participants with hypertension did not change the results. In conclusion, consumption of a DASH-style diet is associated with a marked decrease in kidney stone risk.