We investigate the stability of barium sulphate precipitation in an ideally mixed reactor under stoichiometric conditions. The process is modelled by a population balance equation describing the crystal size distribution coupled with a system of integro-differential equations for the substances in solution. A reduction to a closed moment model is used to analyse the stability of equilibrium solutions. In a certain range of parameters an unstable equilibrium is detected by a numerical calculation of the eigenvalues of the moment system. In this case sustained oscillations of the crystal size distribution are observed in numerical simulations. The numerical results are compared to data obtained from chemical experiments. (c) 2007 Elsevier Ltd. All rights reserved.