Community-acquired bacterial pneumonias are among the most common of infectious diseases. The diagnosis of the etiological agent is becoming more challenging and more critical as new organisms are recognized as pathogens, and as well established agents become increasingly resistant to antimicrobial agents. The value of clinical microbiology laboratory data in the management of pneumonia is controversial. A well recognized, published guideline suggests that no laboratory studies be performed. Yet common practice and a more recent guideline advocate routine collection of sputum for Gram's stain and culture, along with traditional blood work. Given the increasing need to distinguish among a long list of possible pathogens and the need to recognize antibiotic resistance, it seems most prudent to include microbiological studies. This information can be used to guide initial therapy, and perhaps limit the overutilization of broad-spectrum antimicrobials. However, a prerequisite for the use of all cunently available test methods is their deployment in patients for whom there is clinical and radiographic evidence of pneumonia because recovery of a microorganism, especially from sputum, will occur with or without this clinical condition.