This report examines the potential impact on retirement savings of allowing 401(k)-plan participants to invest in private equity (PE). Under most reasonable assumptions, we find that average retirement savings would increase when 401(k) plans include PE investments because PE funds earn higher returns, on average, than public stocks and PE provides diversification opportunities. Under the most optimistic scenario, we estimate that PE investments could boost average account balances by nearly 10 percent over a full career. We also find that simulated impacts vary widely, with some savers doing substantially better than the average and others doing substantially worse.