Vitis vinifera L. cvs. Chardonnay and Merlot shoot cuttings with one inflorescence, either with or without leaves were incubated in the glasshouse. Stilbene phytoalexin synthesis in inflorescences was elicited using yeast extract and phenolic compounds in the flowers were analyzed by HPLC. Quercetin derivatives, caffeyl-and coumaryltartaric acids were the main phenolic components in flowers. Trans-resveratrol was the only stilbene measurable in Chardonnay, while up to seven stilbenic compounds including piceid were found in Merlot. Leaf removal drastically reduced the formation of stilbenes and other phenolics. Since Botrytis cinerea can infect flowers and remain latent inside the developing berry until veraison, a decline in stilbene production potential during bloom may increase primary infections of grapes. The decrease in synthesis of flavonoids and cinnamic acid derivatives may enhance the grapes' susceptibility to damaging UV-B radiation and sunburn.