Recurrent and chronic bacterial pulmonary infection is the major cause of morbidity and mortality in cystic fibrosis (CF). Over 6 months, 72 sputa or oropharyngeal samples were examined from 36 Arab Bedouin CF patients attending Hamad General Hospital, Doha, Qatar. More than 100 pathogens were isolated, mostly Haemophilus influenzae, Staphylococcus aureus and Pseudomonas aeruginosa. Unusual pathogens included Stenotrophomonas maltophilia, Acaligenes xylosoxidans and Mycobacterium abscessus. It is concluded that microbiological biodiversity in the lower airways of CF patients continues to be underestimated and that CF patients harbouring mucoid strains of P. aeruginosa are at a higher risk of acquiring more unusual organisms and probably have a worse prognosis.