The norm of the Riesz projection from to is considered. It is shown that for n=1, the norm equals 1 if and only if p4 and that the norm behaves asymptotically as p/(πe) when p→∞. The critical exponent pn is the supremum of those p for which the norm equals 1. It is proved that 2+2/(2n−1)pn<4 for n>1; it is unknown whether the critical exponent for n=∞ exceeds 2.