Traditional methods of estimating required rates of return overstate hurdle rates in the presence of growth opportunities. We attempt to quantify this effect by developing a simple model which: (i) identifies those companies that have valuable growth opportunities; (ii) splits the value of shares into 'assets-in-place' and 'growth opportunities'; and (iii) splits the equity β into β for 'assets-in-place' and 'growth opportunities'. We find growth opportunities for UK companies over the 1990–2004 period to average 33% of equity value. Incorporating the effect of growth opportunities, the average cost of capital for investment purposes falls by 1.1 percentage points