OBJECTIVE: To describe the case of tonsillary cyst infection with actinomycosis as a diagnostic to be taken into account for the same therapeutic treatment. Correct report case: Male patient 41 years of age, being consultation by 4 months of evolution mild odynophagia, foreign body sensation mobile. Tumor can be seen in the amygdale left for 4 months, 1 cm in diameter, painless, which does not vary in size, and it has frames pharyngotonsillitis 1 - 2 times per year. Denies weight loss, fever, dysphagia, and dyspnea. The notes oroscopy normotophic tonsils, interwar. Viewing rounded tumors in the lower pole of left tonsil, aspect of the cyst, pink, smooth, smooth, painless 1.5 cm, without lymphadenopathy. Classical dissection tonsillectomy performed bilaterally. Returns pathology, right amygdale mild follicular hyperplasia, observed colonies of actinomycosis in the tonsil crypts, left amygdale, and mild follicular hyperplasia with colonies of actinomycosis. CONCLUSION: The actinomycosis infections in head and neck, even though it is rare, it is important that otolaryngologists capable of handling it. A confusing clinical presentation combined with the characterization of the microorganism is difficult to difficult diagnosis. Need a high index of suspicion to make an accurate diagnosis to apply exact treatment.