PURPOSE: A single-center randomized clinical trial was performed to compare postinterventional primary patency rates achieved by cutting balloon angioplasty and high-pressure balloon angioplasty in the treatment of de novo stenoses within autogenous arteriovenous (AV) fistulae for hemodialysis. MATERIALS AND METHODS: Forty-eight patients undergoing their first angioplasty were prospectively randomized to undergo angioplasty with a cutting balloon or high-pressure balloon 4-8 mm in diameter because cutting balloons larger than 8 mm are not available. Nine patients were excluded after angiography, with seven requiring balloons larger than 8 mm. In the remaining 39 patients, there were 42 stenoses in the following regions: juxtaanastomotic (38%), perianstomotic (38%), midcephalic (9%), and cephalic arch (14%). Patients in the cutting balloon group were younger (mean age difference, 9 y; P = .04), but other demographic variables were comparable (range, P = .08-.89). The mean follow-up period was 8.5 mo (range, 24 d to 32 mo). Kaplan-Meier analysis was used to compare duration of patency. Mann-Whitney rank-sum t test and χ2/Fisher exact tests were used to compare continuous and categoric variables, respectively. RESULTS: Technical success was achieved in all 39 patients. At 3, 6, and 12 months, the postinterventional primary patency rates for the cutting balloon group were 61.1% (95% confidence interval [CI], 35.75%-82.70%), 27.7% (95% CI, 9.69%-53.48%), and 11.1% (95% CI, 1.38%-34.71%), respectively, compared with 70.0% (95% CI, 45.72%-88.11%), 42.1% (95% CI, 20.25%-66.50%), and 26.3% (95% CI, 9.15%-51.20%), respectively, for the high-pressure balloon group (P < .3 at each interval). CONCLUSIONS: Compared with high-pressure balloon angioplasty, cutting balloon angioplasty does not improve postinterventional primary patency of de novo stenotic lesions in autogenous arteriovenous fistulae.