Aims: Diagnostic microbiology for community acquired pneumonia (CAP) provides useful information for patient management, infection control and epidemiological surveillance. Newer techniques enhance that information and the time interval for obtaining results. An audit of diagnostic microbiology utilisation, microbiological aetiology, and influence of results on prescribing practices in CAP in a regional Australian hospital setting was performed. Methods: Clinical, microbiological and outcome data were collected by medical record review of patients discharged from Ballarat Hospital with a diagnosis of CAP over a 12 month period. Results: Of 184 identified CAP episodes, 47 (25.5%) had no diagnostic microbiology performed. Respiratory virus polymerase chain reaction (PCR) was rarely performed (2.7% of all episodes). Acute serology was frequently requested, however paired acute and convalescent serology was infrequently performed (5/75 testing episodes; 6.7%). CAP severity was not correlated with microbiological investigation intensity. The most common pathogens identified were Streptococcus pneumoniae and Mycoplasma pneumoniae (5.4% and 2.2%, respectively). Diagnostic testing appeared to rarely influence antimicrobial prescribing. Conclusions: In this setting, diagnostic microbiological tests such as respiratory virus PCR and urinary antigen tests are under-utilised. In contrast, sputum and serological investigations are commonly requested, however rarely influence practice. Interventions to facilitate efficient usage of diagnostic microbiology are required.