The flavour stability of casein and co-precipitated milk proteins has been examined organoleptically. Differences in flavour stability were correlated with processing conditions and the early stages of the non-enzymic browning reaction were implicated in the off-flavour development. The ‘gluey’ flavour present in stored casein could be removed and the flavour stability improved by treatment with activated carbon or Sephadex. However, a better solution to the problem was to avoid the development of off-flavour by careful choice of conditions of preparation, drying and storage to minimize heat damage and browning. Conditions were established under which milk protein could be expected to have flavour stability during at least 6 months storage at ambient conditions.