Nasopharyngeal actinomycosis is a rarely encountered bacterial infection which usually occurs after nasal trauma or surgery. In some clinical cases, nasopharyngeal actinomycosis has appeared in patients without prior trauma, making diagnosis difficult. Here we present three such cases successfully treated with appropriate dosages of penicillin. One 16-year-old boy with no previous medical antecedents showed an important thickening of the posterior wall of the nasopharynx. A similar nasopharyngeal thickening was found in a 42-year-old woman exhibiting poor dental hygiene. In another 42-year-old woman, nasopharyngeal inflammation was accompanied by multiple right lymphoadenopathies. Like the first two patients, the woman had no prior trauma but did exhibit poor dental hygiene and teeth rottenness. In all three patients, actinomycosis diagnosis was confirmed by anaerobic microbial culturing of the biopsy specimen. Although diagnosis is delayed in patients with no prior trauma, treatment with antibiotics has greatly improved the prognosis for all forms of actinomycosis, and neither death nor deformity is common.