Review of taxa comprising the Fissidens bryoides complex in eastern North America shows that they are mere variations of a structurally very diverse species, F. bryoides. Probable factors influencing the expression of the variations are indicated. Lectotypes are designated for F. viridulus var. brevifolius, F. exiguus var. falcatulus and F. texanus. Synonymy for F. bryoides in eastern North America is given. The Fissidens bryoides complex in eastern North America includes the following taxa of section Bryoidium C. Miill. (Grout, 1943): 1) F. bryoides and its variety incurvus; 2) F. viridulus and its varieties tamarindifolius and brevifolius (= F. bryoides var. brevifolius (Ren. & Card.) Wijk & Marg., 1960); and 3) F. minutulus. Although relegated to section Semilimbidium C. Miill. (= subsection Semilimbatus Grout, 1936, pro parte; = section Semilimbatus Grout, 1941, pro parte), F. exiguus and its variety falcatulus, and F. andersonii also belong to this complex.