The Pennsylvanian System in Iowa includes strata ranging from Morrowan to Virgilian in age. Based primarily on core studies, the palynology of coals has formed the basis for refinement of stratigraphic correlations through the dominantly non-marine Lower and Middle Pennsylvanian sequence, and has permitted formational subdivision of the complex Cherokee Group. The palynological characteristics of the major coals and coal-bearing units are described in detail. The sequence of miospore appearances and extinctions permits close correlation of Iowa coals to coals of the Illinois Basin. In addition, the miospore stratigraphy of Iowa coals corresponds strongly to published zonations for the Upper Carboniferous coal-bearing strata of western Europe and the Soviet Union. In recognition of serious problems that exist in the application of standard Midcontinent Pennsylvanian chronostratigraphic nomenclature to the Iowa section, practical means for distinction of Morrowan, Atokan and Desmoinesian strata are proposed to facilitate regional correlations. The extinction of Schulzospora rara is used to mark the top of the Morrowan Series, and the extinction of Dictyotriletes bireticulaius is considered to indicate the top of the Atokan. 314 species assigned to 111 genera are documented and illustrated, and their observed occurrences in the Iowa section are summarized. Three new genera, Anacanthotriletes, Anafoveosporiies and Dictyomonolites are proposed: the diagnoses of five genera. Apiculatasporites Ibrahim 1933, Reiiculitriletes Madler 1964, Sinuspores Artiiz 1957. Dictyotrileies Naumova ex Potonié and Kremp 1954 and Spackmanites Habib 1966 are emended to reflect new interpretations of their morphology. Thirteen new species are described, and thirteen other new names are proposed to correct or avoid homonymies. Several other genera are reviewed and new combinations proposed.