Monomeric　green　tea　catechin　(GTC)　and　oligomeric,　oxidized　black　tea　phenolic　(BTP)　have　shown　promising　health　benefits,　although　GTC　has　been　more　extensively　studied　than　BTP.　We　review　the　current　knowledge　on　bioavailability,　colonic　transformation,　and　gut　microbiota　modulatory　effects　of　GTC　and　BTP.　As　a　result　of　their　similar　poor　bioavailability　in　the　small　intestine　and　potentially　similar　metabolites　upon　colonic　fermentation,　it　seems　as　if　GTC　and　BTP　have　similar　health　effects,　although　it　cannot　be　excluded　that　they　have　different　gut　microbiota　modulatory　effects　and　that　BTP　gives　a　poorer　yield　of　bioactive　phenolic　metabolites　upon　colonic　fermentation　than　GTC.　©　2018　American　Chemical　Society.