Foraminifera from the Yorktown formation (upper Miocene) of the York-James Peninsula, Virginia, are described. Ecologically, the Yorktown faunas prove to be from the upper and middle neritic as defined by Ladd, Gunter, and Revelle. The mollusk zonations, principally established by Mansfield and Gardner, seem to have little or no validity from either the mollusk or foraminiferal viewpoint. The age of the Yorktown formation appears to be topmost Miocene. Of 108 species of Foraminifera figured and described from the Yorktown, 29 forms are either new or require new names to set them off from forms erroneously identified with them in previous works. Taxonomic problems dealing with Eponides, Buccella, and the Globigerinidae are discussed. One new genus, Rectocibicidella, is described. Some results of studies of the pre-Yorktownian Miocene of the peninsula are given, including the zonations revealed by Bolivina floridana and Siphogenerina lamellata. Cross-sections are given, constructed from available subsurface data, and the extent of the formation is discussed.