Background— Studies of the effect of right ventricular ejection fraction (RVEF) on outcomes in heart failure (HF) are limited by small sample size and short follow-up. Methods and Results— We examined the effect of baseline RVEF on outcomes in 2008 Beta-Blocker Evaluation of Survival Trial (BEST) participants with HF and left ventricular ejection fraction ≤35% during 24 months of mean follow-up. RVEF, estimated by gated-equilibrium radionuclide ventriculography, was used to categorize patients into 4 RVEF groups: ≥40% (n=733), 30% to 39% (n=531), 20% to 29% (n=473), and <20% (n=271). Unadjusted rates for all-cause mortality in patients with RVEF ≥40%, 30% to 39%, 20% to 29%, and <20% were 27%, 32%, 35%, and 47%, respectively. When compared with patients with RVEF ≥40%, unadjusted hazard ratios and 95% confidence intervals for all-cause mortality for those with RVEF 30% to 39%, 20% to 29%, and <20% were 1.19 (0.97 to 1.46; P =0.087), 1.45 (1.17 to 1.78; P =0.001), and 1.98 (1.59 to 2.47; P <0.0001), respectively. Respective multivariable-adjusted hazard ratios (95% confidence intervals) for all-cause mortality associated with RVEF 30% to 39%, 20% to 29%, and <20% were 1.07 (0.87 to 1.32; P =0.518), 1.12 (0.89 to 1.40; P =0.328), and 1.32 (1.02 to 1.71; P =0.034), respectively. Adjusted hazard ratios (95% confidence intervals) for other outcomes associated with RVEF <20% (compared with ≥40%) were as follows: cardiovascular mortality, 1.33 (1.01 to 1.76; P =0.041); HF mortality, 1.61 (1.03 to 2.52; P =0.037); sudden cardiac death, 1.29 (0.87 to 1.91; P =0.212); all-cause hospitalization, 1.21 (1.00 to 1.47; P =0.056); and HF hospitalization, 1.39 (1.10 to 1.77; P =0.007). Conclusions— Baseline RVEF <20% is a significant independent predictor of mortality and HF hospitalization in systolic HF.