The mid-Tertiary sequence in southwestern Puerto Rico has been divided into two formations, the Juana Diaz Formation at the bottom and the Ponce Limestone at the top. The Ponce Limestone is further subdivided into two unnamed members. The two formations have not been defined properly and no type sections have been designated. The lack of definitions, combined with complex stratigraphic relations resulting from complex structural relations and extensive facies changes, and inadequate regional studies, has led to major discrepancies in the designation of the mid-Tertiary stratigraphic units. The term "lower member of the Ponce Limestone," for example, has been applied to stratigraphic units that span the entire stratigraphic range of the mid-Tertiary sequence. The current s ratigraphic terminology is reviewed and evidence for the discrepancies is presented. The present mid-Tertiary stratigraphic terminology is unsatisfactory, and further regional stratigraphic and paleontologic studies are needed before meaningful stratigraphic names can be applied to the mid-Tertiary sequence in southwestern Puerto Rico.