Atypical bacteria play role in infection of upper respiratory tract in adults. The most often bacteria playing role in these infections are Chlamydophila pneumioniae and Mycoplasma pneumoniae. These bacteria have significant impact in pharyngitis and tonsillitis and less in rhinosinusitis. Atypical bacteria can cause infection of the upper respiratory tract as a single pathogen or one of the pathogens. Mycoplasma pneumoniae most often is s a single causal factor of the disease, when Chlamydophila pneumoniae most often co-exists with infection with other pathogens. Majority of infections of upper respiratory tract in adults caused by atypical bacteria has mild history with insignificant sings and symptoms. Suspicion of the disease can be recurrent history of disease or absence of recovery after standard treatment.