The antimicrobial activity of lidocaine in bronchoalveolar lavage fluid (BAL(f)) was investigated. Clinical respiratory isolates were added to BAL(f) suspensions containing lidocaine and to normal saline. The growth of two of four isolates of Streptococcus pneumoniae was significantly reduced in the presence of lidocaine-BAL(f) compared with controls in saline. Growth of Moraxella catarrhalis isolates was reduced in normal saline when compared with BAL(f) containing lidocaine. There was no effect upon the growth of Haemophilus influenzae, Pseudomonas aeruginosa and Candida albicans isolates. The recovery of isolates of S. pneumoniae may be reduced below the critical threshold of 10(5) cfu/mL during bronchoscopy when using lidocaine as a local anaesthetic.