The preparation of yoghurt from milk concentrated by reverse osmosis to 12.5 and 15.0 per cent TS was compared with that from milk adjusted to comparable concentrations by the addition of skim milk powder. Culture growth, acid production, acetaldehyde production, viscosity and flavour scores of yoghurt prepared from the reverse osmosis concentrates were at least equal to those of yoghurt prepared from conventionally concentrated milk, suggesting that the former constitutes a suitable yoghurt base.