Bacterial endosymbionts are known residents of many insect species. It is believed that these symbiotic relationships contribute to nutritional fitness of the insect and may play a role in speciation. Primary prokaryotic endosymbionts of whiteflies are Gammaproteobacteria and housed in specialized insect cells called bacteriocytes. We have examined individuals from over 50 different species of whiteflies primarily from North America and Australia using PCR amplification and direct sequencing of the products produced from primary symbiont 16S ribosomal DNA (rDNA) genes. Many species yielded a mixture of PCR products that were not suitable for direct sequencing. These samples have been cloned and sequenced to generate usable sequence information. Maximum parsimony analysis and congruence between the phylogeny of the symbionts and their insect hosts were examined. The diversity and/or abundance of organisms in the bacteriomes and bacteriocytes will be discussed.