The study was conducted to identify the types of Gramnegativernpharyngeal bacilli and to determine their prevalencernand antibiotic susceptibilities.rnOne~thousand pharyngeal sHab specimens were processed:rn300 from students, 303 from adult employees of Berhanena-Â·rnSelam Printing Press (BSP), 200 from hospital staff and 197rnfrom patients. The isolates were iden'tified by standardrnbiochemical tests. All isolates were tested for theirrnsensitivities to 11 antibietics using the Kirby-Bauer technique.rnForty-five (15%) students, 53 (17.5%) employees of BSP,rn27(13.5%) hospital staff and 54(27.4%) patients were carriersrnof one or more Gram-negative bacilli (GNB).rnThe pharyngeal carriage rates of GNB were similar amongrnthe various groups of healthy subjects (P>O.l) but they werernlower than that of the patients (peO.Ol). The increase inrnprevalence vIaS not correlated to antimicrobial therapy, butrnseems to be associated vlith underlying disease and durationrnof hospitalization. There was no association between isolationrnrates of GNB and age or sex.rnTwo hundred and nineteen strains of more than 18 speciesrnof Enterobacteriaceae or nonfermenting Gram-negative bacillirnwere isolated. Colony counts of these organisms were lowerrnamong healthy subjects than among pa'tients. Klebsiella Vias most frequently ir;olated (37%), followed by _~seudo2!'-0Tl_a.? (13.2%),rn-E-n-te-r-o-b-a"ct-e-r (12.8%) and -A=c-i-n--e-t-o-b-a_c ... -t-e--r (10%). Others werernless frequently isolated. The frequency of isolation ofrnKlebsiell~ was higher from students (49%) than from the otherrnthree study groups (32.5%; P