In this volume diatoms of the genus Pinnularia from the Great Xing'an Mountains (in northeastern China), a very pristine region with a great diversity of habitat types, are described. A Total of 89 taxa of the genus Pinnularia were studied and documented in both light and scanning electron microscope images. AS a result 19 new species are proposed, and 7 neotypes of taxa of Skvortzow are designated. THe diatom genus Pinnularia is notoriously difficult taxonomically, with populations having small numbers and apparently great intraspecific phenotypic variability. P.T. CLeve (1895, p. 72) wrote, "The fresh-water forms pass into one another to a great extent, so that the definition of good or distinct species or groups is a matter of greatest difficulty or almost impossible." One of the parts of the world where the freshwater diatom flora is relatively unknown is China. THis work will contribute significantly to our understanding of the diversity of the genus Pinnularia overall, and especially in China.