Upper respiratory tract (URT) infections are common and account for more medical visits than any other type of infectious disease. Diagnostic procedures for the following syndromes are included in this report: Streptococcal and nonstreptococcal pharyngitis, laryngeal syndromes, otitis, sinusitis, and others caused by unusual and/or uncommon bacteria or fungi, including Lemierre's disease, Vincent's angina, pharyngeal and peritonsillar abscesses, diphtheria, candidiasis, and zygomycoses. Detailed information is provided on specimen collection and processing, selection of laboratory tests, interpretation of findings, reporting results, additional procedures for uncommon infections, and the use of new techniques. All the information included in this article is contained in the Standard Operating Procedures for Clinical Microbiology (http://www.seimc.org/protocolos/microbiologia/).