The population diversity of cultured isolates of the phylum Bacteroidetes was investigated from salt-marsh sediments. A total of 44 isolates that belonged to this phylum were isolated either from high-dilution plates or from end-dilution most-probable-number (MPN) tubes. The majority of the isolates came from Virginia, with others isolated from salt marshes in Delaware and North Carolina. All the isolates were aerobic Gram-negative, catalase positive small rods that formed uniform colonies; most had either yellow or orange pigmentation. Riboprinting of 40 isolates revealed they were genotypically diverse, consisting of 33 different riboprint patterns; there were four riboprint groups with two or more members. The isolates could be divided into 23 different fatty acid methyl ester (FAME) profiles at the species level with 14 of the profiles being unique to single isolates. One group of 10 isolates was closely related, suggesting this group may be well adapted for life in salt marshes. Thirteen of the isolates were selected for sequencing of the small-subunit ribosomal RNA gene representing a diverse group of isolates that fell within the classes Sphingobacteria and Flavobacteria. Only one of the isolates was >97% similar at the 16S rDNA to a described species of Cytophaga marinoflava; the other isolates were 94 to 96.5% related to undescribed isolates mostly within the class Flavobacteria. There was good concordance between the FAME dendrogram and a phylogenetic tree based on comparison of 16S sequences. There were no obvious temporal or spatial distribution patterns to the isolates, suggesting that this group of bacteria is inherently diverse.