The fastness to washing of some natural dyestuffs has been assessed. Tests have been carried out under standard conditions (50°C) and also at 20°C with a washing formulation used in conservation work on ancient textiles. A number of the dyestuffs undergo marked changes in hue on washing and this is shown to be due to the effect of even small amounts of alkali in washing mixtures. The necessity of knowing accurately the pH of alkaline solutions for the cleaning of textiles dyed with natural dyestuffs is highlighted.