The relative floral anthocyanidin contents of 195 commercial petunias with floral colours other than white and yellow were determined using HPLC, and the presence of five anthocyanidins (cyanidin, peonidin, delphinidin, petunidin, and malvidin) was confirmed. Pelargonidin was not detected, and delphinidin was not a major component. Using a principal component analysis of the relative anthocyanidin contents, the petunias were classified into three phenotype-groups accumulating cyanidin, peonidin, or malvidin, (plus petunidin) as the major anthocyanidin. A fourth phenotype was segregated in the progeny obtained by self-pollinating an F1 hybrid of the malvidin group; this accumulated delphinidin 3-glucoside in a markedly crumpled corolla-limb (delphinidin group). Such inferior floral traits, associated with the accumulation of delphinidin 3-glucoside, are thought to be the driving force that removed the delphinidin group from commercial petunias. A comparison of flowers of the delphinidin group and those of the other groups may provide a useful tool towards a deeper understanding of how anthocyanin biosynthesis relates to normal development of the corolla.