Phlorin (3,5-dihydroxyphenyl beta-D-glucopyranoside), an orange peel marker, has been searched in 45 species and varieties of Citrus. The phlorin content was determined by high-pressure liquid chromatography in juices and aqueous peel extracts of these different fruits. The phlorin content in C. reticulata peel extract varies from 0 to 1012 mg L(-)(1) with a mean of 162 mg L(-)(1). On the contrary, phlorin was not found in mandarin and clementine juices except for mandarin "Commune" and "Beauty" (33 and 30 mg L(-)(1), respectively). In the 14 species of oranges and varieties, phlorin was detected in juices and peel extracts with a mean of 22 and 492 mg L(-)(1), respectively, while for grapefruits, means were 108 mg L(-)(1) in juices and 982 mg L(-)(1) for peel extracts. Tangors and tangelos which are hybrids (C. reticulata x C. sinensis and C. reticulata x C. paradisi, respectively) are characterized by the systematic presence of phlorin in peels (mean: 406 and 659 mg L(-)(1), respectively) while in juices its presence could be variable (0-73 mg L(-)(1)). These heterogeneity and values may be explained by the genetic variability of these hybrids and the phlorin content of their parentage group.