© 2018 by the American Society of Nephrology. Background and objectives Postoperative ultrasound is commonly used to assess arteriovenous fistula (AVF) maturation for hemodialysis, but its utility for predicting unassisted AVF maturation or primary AVF patency for hemodialysis has not been well defined. This study assessed the predictive value of postoperative AVF ultrasound measurements for these clinical AVF outcomes. Design, setting, participants, & measurements We queried a prospective vascular access database to identify 246 patients on catheter-dependent hemodialysis who underwent AVF creation between 2010 and 2016 and obtained a postoperative ultrasound within 90 days. Multivariable logistic regression was used to evaluate the association of clinical characteristics and postoperative ultrasound measurements with unassisted AVF maturation. A receiver operating characteristic curve estimated the predictive value of these factors for unassisted AVF maturation. Finally, multivariable survival analysis was used to identify factors associated with primary AVF patency in patients with unassisted AVF maturation. Results Unassisted AVF maturation occurred in 121 out of 246 patients (49%), assisted maturation in 55 patients (22%), and failure to mature in 70 patients (28%). Using multivariable logistic regression, unassisted AVF maturation was associated with AVF blood flow (odds ratio [OR], 1.30; 95% confidence interval [95% CI], 1.18 to 1.45 per 100 ml/min increase; P<0.001), forearm location (OR, 0.37; 95% CI, 0.08 to 1.78; P=0.21), presence of stenosis (OR, 0.45; 95% CI, 0.23 to 0.88; P=0.02); AVF depth (OR, 0.88; 95% CI, 0.77 to 1.00 per 1 mm increase; P=0.05), and AVF location interaction with depth (OR, 0.50; 95% CI, 0.28 to 0.84; P=0.02). The area under the receiver operating characteristic curve, using all these factors, was 0.84 (95% CI, 0.79 to 0.89; P<0.001). Primary AVF patency in patients with unassisted maturation was associated only with AVF diameter (hazard ratio, 0.84; 95% CI, 0.76 to 0.94 per 1 mm increase; P=0.002). Conclusions Unassisted AVF maturation is predicted by AVF blood flow, location, depth, and stenosis. AVF patency after unassisted maturation is predicted only by the postoperative AVF diameter.