Tea leaf contains very high level of polyphenols, mostly flavonoids, which distinguishes it from other plants. These flavonoids and their oxidative products formed during fermentation and drying, largely determine the color and taste of black tea. We studied the flavonoid content of various clones of tea and found it to correlate with chalcone synthase activity in the tea leaf. Induction of chalcone synthase (CHS) activity in the tea leaf was observed during the second flush, a period where flavonoids content of tea is highest in Assam. Expressions of enzymes viz. Cinnamyl alcohol dehydrogenase (CAD), cinnamyl CoA reductase (CCR) and Peroxidase (POD) involved in the synthesis of lignin were depressed during the second flush. These observations suggest that CHS may be a key enzyme involved in catechin biogenesis in tea leaf.