Clinical microbiology has lagged behind other laboratory disciplines in the speed with which specimens are processed and results generated. If early specific microbiological diagnosis is achieved and antimicrobial therapy is initiated quickly, a better outcome for the patient can be expected. Because of the time required for traditional cultural methods, approaches to rapid diagnosis have included chemical stains, immunological assays and, more recently, nucleic acid detection performed directly on clinical samples. Some procedures in microbiology have attempted to reduce the time to the detection of culture positivity whereas others have used a combination of both rapid culture and immunological detection - as with shell vial assays for cytomegalovirus. The time of the technologist is one of the major cost factors in laboratory medicine and, with the current economic climate and efforts towards cost-containment, is a major incentive for rapid methodology. However, such methods must be evaluated carefully before introduction - clinical relevance, sensitivity and specificity of detection must not be compromized by rapid turn-around time.