ABSTRACT: The present paper is an inventory of the biostratigraphical ammonite data at the boundaries of the Sinemurian and Pliensbachian Stages and of the Lower-Upper Pliensbachian Substages. Sinemurian and Pliensbachian Stages belong to the Early Jurassic (Lias) and the age of their boundary is 190 m.y. following the last version of the Geologic Time scale compiled by Walker and Geissman (2009). Since 2006, the Global boundary Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage is formally defined at Wine Haven in Yorkshire Coast (UK). This level coincides with the ammonite association Bifericeras donovani Dommergues and Meister and Apoderoceras sp. which define the base of the Taylori Subchronozone of the Jamesoni Chronozone. For the Lower-Upper Pliensbachian boundary, estimated at 186.5 m.y. there is no formal definition with a GSSP until now. Several options remain open as well in the Euroboreal Domain (Hebrides, Yorshire, Dorset in UK, Causses Basin in France, Cordillera Iberica in Spain, Lusitanian Basin in Portugal) as in the Tethyan Domain (Subbeticas in Spain, Apennines in Italy, Bakony in Hungary). Worldwide correlations (Euroboreal, Tethyan and East Pacific Domains) at these boundaries are proposed based on ammonites after critical review of their taxonomy and biostratigraphy. Indeed for Lower Jurassic, ammonites represent the best fossil group for precise biostratigraphy and correlation and that is why the standard chronostratigraphic framework (at zonal level) has been based on them since Oppel (1856-58).