Branhamslla, catarrhalas. previously known as Neisssria catarrhalas and as a respiratory commensal, was recognized since early 80'ies as a pathogen capable on many occasions to produce B-lactamase and resist penicillin and related antibotics. A study was undertaken to evaluate this emerging respiratory pathogen and aiming to find out the rate of infection,clinical and radiological features and related epidemiological data of the patients. In addition, microbiologic characterization and the rate of B-lacatamase production and antibiotic resistance pattern were also studied. For the period from October 1995 to April 1996; a total of 300 expectorated sputum samples were collected from patients with productive cough at the University Hospital-Saddam College of Medicine. Selective cellular criteria were used, so that 262 (87.3%) were acceptable, and 205 (78.2%) were bacteriologically positive by Gram stain directed culture method and/or Ziehl-Noolsen's stain. Branhamella catarrhalis was found to be the third most frequently isolated bacterial pathogen; isolated from 26 sputum samples (representing 9.29% of the acceptable and 12.68% of the positive ones).It was noted that the peak of isolation among other pathogens was during November (21.88%).Branhamella. Gatarrhalis was purely isolated in 17/26 (65.38%) and mixed with other pathogens in 9/26 (34.62%).No difference was noted between males and females in incidence: 13 (50%) for each. Most of the patients (73,0%) were elderly above 50 years and of average age (61.08) years;having an underlying chronic cardiopulmonary disorder (96.15%) and were cigarette smokers (73.08%). Acute exacerbation of the underlying disorder was provisionally diagnosed in 84.62%. pneumonia in 11.54% and acute bronchitis in 3.85%. The features of the underlying disorder were predominant in the patients in general and chest x-ray findings were non-specific. Microscopically; B.catarrhalis appeared as Gram-negative diplococci intra- and extraleukocytic in sputum smears. All other microbiological features were as typical as descriptions. Two tests; modified DNase (with toluidine blue) and Tween-80 hydrolysis, were found to be substitutable for each other as reliable confirmatory tests to differentiate B.catarrhalis from Neisseria spp. It was found that B.catarrhalis capable to surviye in dry atmosphere at room temperature on cloth material for 48 hours. Branhamella catarrhalis was isolated from 9/200 (4.5%) of oropharyngeal swabs; 2/79 (2.53%) were from healthy controls and 7/121 (5.79% from the risk group (with an underlying chronic cardiopulmonary disorder and/or an immunosuppressive factor). A Branhamella specific (acetazolamide containing) medium was used for this purpose. B-lactamase was produced by 29/35 (82.86%) of the isolates, 22/26 (84.62%) of the patients and 7/9 (77.78%) of the carriers All isolates were resistant to penicillin G. ampicillin and amoxicillin by disc diffusion susceptibility testing.Two isolates (5,71%) were insensitive and 5 (14.29%) intermediately sensitive to cephalexin. All of the isolates (100%) were sensitive to erythromycin,tetracycline,doxycycline,chloramphenicol gentamicin and ceftizoxitme.