Appropriate laboratory investigations of a CAP patient depend upon whether the patient is treated in or out of hospital, with outpatients requiring no further microbiological tests. However, North American recommendations for microbiologic assessment of inpatients include sputum Gram stain and culture, and blood cultures. European recommendations differ, recommending blood cultures only in high-risk patients, and Gram stains only in good specimens. If a patient has severe CAP, Legionella antigen testing needs to be performed. Pneumococcal antigen screening is recommended in the US, which also advocates culture and testing of pleural fluid in patients with pleuritis, as well as HIV testing. In my opinion pneumococcal antigen testing is a research tool. With the advent of the SARS epidemic, other pathogens need to be looked for, with recent results indicating the Coronavirus has been identified in approximately 5% of CAP patients.