  We discuss the extraction of negative-parity baryon masses from lattice QCD
calculations. The mass of the lowest-lying negative-parity $J = 1/2^{-}$ state
is computed in quenched lattice QCD using an ${\cal O}(a)$-improved clover
fermion action, and a splitting found with the nucleon mass. The calculation is
performed on two lattice volumes, and three lattice spacings enabling a study
of both finite-volume and finite-lattice-spacing uncertainties. A measurement
of the first excited radial excitation of the nucleon finds a mass considerably
larger than that of the negative-parity ground state, in accord with other
lattice determinations but in disagreement with experiment. Results are also
presented for the lightest negative-parity $I=3/2$ state.
