This study represents a taxonomic survey of class Bacillariophyceae diatoms found in samples collected in the Iguaçu River (Iguaçu National Park, municipality of Foz do Iguaçu, in the state of Paraná, Brazil) between August 2007 and July 2008. Two sampling stations were utilized, the first located upstream of Iguaçu Falls (Cais Bananeiras Station) and second downstream of the falls (Cais Macuco Safari Station). The study resulted in the identification of 86 taxa, including 74 at the specific level and seven taxonomic varieties. Two of these had never before been documented in the state of Paraná: Gomphonema gibberum Hustedt and Pinnularia meridiana Metzeltin & Krammer. Nine are first-time records for Brazil: Cymbella charrua Metzeltin, Lange-Bertalot & García-Rodríguez, Placoneis ovillus Metzeltin, Lange-Bertalot & García-Rodríguez, Gomphonema affinopsis Metzeltin, Lange-Bertalot & García-Rodríguez, , Gomphosphenia lingulatiformis (Lange-Bertalot & Reichardt) Lange-Bertalot, Luticola aequatorialis (Heiden) Lange-Bertalot & Ohtsuka, Sellaphora garciarodriguezii Metzeltin & Lange-Bertalot, Eolimna submuralis (Hustedt) Lange-Bertalot Kulikovskiy, Geissleria neosubtropica Metzeltin, Lange-Bertalot & García-Rodríguez and Stauroneis cf. sylviabonillae Metzeltin, Lange-Bertalot & García-Rodríguez.
taxonomy; microalgae; lotic system; state of Paraná