This paper deals with the biostratigraphic significance of nannofossil species recorded from some Maastrichtian rocks in the Eastern Desert, Upper Egypt. Careful study of these calcareous nannoflora and their stratigraphic occurrences have resulted in precise dating of the different rock units, and in further refinement of the nannobiozonal schemes still vaguely defined in Egypt. Four nannobiostratigraphic zones might be established, arranged from the base to top as: Quadrum trifidum zone (Campanian-Maastrichdan), Arkhangelskiella cymbiformis zone (early-middle Maastrichtian), Lithraphidited quadratus zone (middle-late Maastrichtian) and Nephrolithus frequens zone (most late Maastrichtian). Such Maastrichtian nanno-biozones are easily equated with the planktonic foraminiferal Globotruncana, fornicate zone, Globotruncana gansseri zone and Globotruncana esnehensis zone of the same succession. Their occurrences in other parts of Egypt as well as in different parts of the world indicate that they could be successfully used for biozonation and transoceanic correlation. The succession was divided into distinct litho and biostratigraphic units related mostly to Campanian-Maastrichtian and Maastrichtian ages. Besides, microfacies studies on thin sections representing Duwi phosphate and L. Dakhla Shale formations were carried out. The paleoenvironmental conditions that prevailed during sedimentation were interpreted in accordance.