Individual florets (4–5 mm long) of a purple cultivar (Fandango) of the horticultural chrysanthemum (Chrysanthemum morifolium Ramat) were taken from flower buds just prior to opening and cultured in a sterile liquid medium (containing inorganic salts and sucrose) at 15 °C under a 12-h day. For the first 14 days increase in wet weight was exponential. Anthocyanin appeared on the third day and was then synthesized rapidly. Chlorophyll and carotenoid were present initially: carotenoid levels rose quickly while chlorophyll remained almost constant. Highest pigment content and most growth were found when the florets were grown on 3 per cent sucrose. However, the highest anthocyanin concentration was found with 4 per cent sucrose, the highest carotenoid concentration with 0.6 per cent sucrose. No anthocyanin was produced when the florets were grown at 6 or 30 °C; maximum yield was at 15 °C. Most carotenoid was formed at 30 °C and most chlorophyll was found at 20–5 °C. All florets from 1 to 7 mm long could be cultured. These results are discussed in relation to flower colour and pigment formation in vivo.