Remarkable diversity of diatom taxa occurs in intertidal sand-flats of the Nakdong River estuary, one of the most dynamic and productive ecosystem in Korea. Benthic diatoms were collected from the sandy sediments to clarify the taxonomic accounts and distribution of the old genus Navicula, i.e., the naviculoid flora. Total 92 taxa belonging to Navicula sensu stricto and 22 genera separated from Navicula sensu lato are reported with brief descriptions and micrographs, and many species remain unidentified. The genera are ranked by the number of diatom species: Navicula of 33 species and varieties, Fallacia of 17 species, Placoneis of five species, Fogedia and Parlibellus of four species, Austariella, Hippodonta and Petroneis of three species, Cosmioneis, Diadesmis, Luticola, Moreneis and Sellaphora of two species and variety, Berkeleya, Chamaepinnularia, Cocconeiopsis, Diademoides, Dickieia, Eolimna, Geissleria, Haslea, Lyrella and Mayamaea of one species. Through 32 samplings of the 12 areas, the important species were identified Navicula perminuta, N. gregaria, N. torneensis, Fallacia cunoniae, F. litoricola, F. subforcipata, F. tenera. The naviculoid diatoms constitute an average of 27% (range: minimum to maximum, 5-75%), of the benthic diatom assemblages. The diatom assemblages are characterized by the colonizing of a few dominant or frequent species and many occasional or rare species. The dominant species were observed to fluctuate with sampling site and time. Among the reported naviculoid diatoms, 46 taxa are newly reported in Korea.