Myiasis is the infestation of living vertebrates or humans tissues by dipterous larvae. The oral cavity is rarely affected by this infestation and the circumstances which can lead to oral myiasis include persistent mouth opening together with poor hygiene. Such infestations have been reported mainly in developing countries such as in Asia. Although rare, nosocomial myiasis must be noted carefully, especially in case of hospitalized patients. This report describes three cases of nosocomial oral myiasis in hospitalized patients in ICU (intensive care unit) in Tabriz, North West of Iran.