Pinocembrin (5, 7-dihydroxyflavanone) is a flavanone extracted from the rhizome of Boesenbergia pandurata.Our previous studies demonstrated that pinocembrin had no toxicity or mutagenicity in rats. We here evaluatedits effects on the initiation and promotion stages in diethylnitrosamine-induced rat hepatocarcinogenesis, usingshort- and medium-term carcinogenicity tests. Micronucleated hepatocytes and liver glutathione-S-transferaseplacental form foci were used as end point markers. Pinocembrin was neither mutagenic nor carcinogenic inrat liver, and neither inhibited nor prevented micronucleus formation as well as GST-P positive foci formationinduced by diethylnitrosamine. Interestingly, pinocembrin slightly increased the number of GST-P positive fociwhen given prior to diethylnitrosamine injection.