Based on the specific plaque theory in periodontology, several chairside tests have been introduced for the microbiological examination of periodontal patients. For the majority of these patients, however, a standard therapy (root planing in combination with good oral hygiene) results in a favorable outcome. Therefore, only for a small minority of periodontal patients a microbiological analysis could possibly contribute to better treatment. For such patients, a choice can be made between a culture technique (which is labour intensive and has a long waiting time before an answer is available) and one of the chairside tests. The culture technique has the advantage to examine most of the flora. The chairside tests have the advantage of giving immediate results, but are limited to a small number of species or morphotypes. As long as the outcome of a microbiological examination in general cannot be translated into a more specific treatment strategy, the frequent use of microbial analyses should not be advocated. Since the validity of the chairside tests have yet to be fully examined through clinical trials, culturing should be the method of choice, because their antibiogram could lead to a more specific antibiotic therapy for the few patients in need.