Throughout the past several years molecular pathology has played an increasingly important role in diagnosis and management of disease. Current molecular methods include genetic testing, epidemiologic studies, tissue typing, in situ hybridization, forensics, parentage testing, and detection, identification, and classification of microorganisms. Arguably the leading area for application of molecular methods has been in the diagnosis and monitoring of infectious diseases. Molecular techniques used in microbiological diagnosis include nucleic acid amplification techniques, DNA sequencing and typing, direct molecular probe techniques (in situ hybridization), and nucleic acid quantitation. Commercially available reagents, equipment, and test kits enable implementation of this technology in the clinical laboratory.