Identifications were made on 2990 isolates of gram-negative bacteria from 702 samples of commercial raw cotton fiber from the Texas-Oklahoma and Western cotton-producing regions in the crop of 1987. The objective was to establish a reliable profile of the kinds of gram-negative bacteria on the fiber against which the gram-negative bacterial population on any new sample of interest in respect to causation of byssinosis could be evaluated. The most commonly encountered bacteria on the samples examined and reported on here were Enterobacter agglomerans, E. cloacae, Pseudomonas putida, P. syringae, and members of the Pseudomonas-like VE group. Less frequently encountered were P. aeruginosa, P. fluorescens, P. Paucimobilis, P. pickettii, P. stutzeri, P. alcaligenes, P. pseudoalcaligenes, and P. vesicularis. Also infrequently detected were Acinetobacter calcoaceticus, Enterobacter sakazakii, Escherichia coli, Flavobacterium odoratum, and Klebsiella planticola/oxytoca. Coryneform bacteria were detected in some samples. No clear and certain evidence of major geographical localization or concentration of any genus or species in any part of the total area involved in the present study was seen. Suggestions are made in respect to the use of the background bacterial profile in practical byssinosis situations.