An upper Aptian to Cenomanian sedimentary succession containing unusually well-preserved planktonic foraminifers was documented during ODP Leg 171B, which was devoted to the study of the Blake Plateau off Florida. With the exception of two zones within the Albian, an almost continuous composite section permits detailed investigation of the evolution of the foraminiferal assemblages. Emphasis in this paper is placed on the Aptian/Albian and Albian/Cenomanian transitions. In addition, the excellent preservation of the material enables some taxonomic revision, mainly on the basis of wall microstructural characters, of several planktonic foraminiferal lineages and taxa, such as the Hedbergella praetrocoidea-H. trocoidea-Ticinella eubejaouaensis phylogenetic relationship and the Rotalipora globotruncanoides or Hedbergella rischi species concepts.