We report the observation of acid-fast Cyclospora cayetanensis oocysts in a sputum sample. The patient, a 60 year-old, HIV negative man, was successfully treated for pulmonary tuberculosis during 1997. On February 1998, he was admitted to our center due to loss of weight, cough with purulent expectoration, dysphonia and a radiological picture of pulmonary fibrosis. Bacilloscopic study of sputum (negative for acid-fast bacilli) stained with Ziehl-Neelsen technique showed large (8-10 µm) spherical, acid-fast Cyclospora cayetanensis oocysts. No other pathogens were isolated on cultures from this sample or from laryngeal biopsy. Serial parasitologic studies showed C. cayetanensis and also eggs of Trichuris trichiura, Ascaris lumbricoides and Hymenolepis nana and of Entamoeba coli cysts. The patient lives in the outskirts of Buenos Aires in a brick-made house with potable water and works as builder of sewers. He travelled in several occasions to the rural area of province of Tucumán which has poor sanitary conditions. C. cayetanensis is an emergent agent of diarrhea and as far as we know this is the first time the parasite is observed in respiratory samples.Comunicamos a observação de grandes oocistos (8-10 µm de diâmetro) esféricos, ácido-álcool-resistentes de Cyclospora cayetanensis em amostra de escarro corada com a técnica de Ziehl-Neelsen. Na amostra não foram observados nem cultivados outros agentes patogênicos. Trata-se de um paciente do sexo masculino, 60 anos de idade, HIV (-), tratado previamente para tuberculose pulmonar (1997). Em fevereiro de 1998 apresentou-se em nosso hospital com perda de peso, tosse com expectoração purulenta, disfonia e imagens radiológicas de fibrose pulmonar. As culturas das amostras de escarro e da biopsia de laringe foram negativas. O exame parasitológico seriado de fezes mostrou ovos de Ascaris lumbricoides, Hymenolepis nana e Trichuris trichiura e cistos de Entamoeba coli. O paciente mora nos arredores de Buenos Aires numa casa de alvenaria com água potável e é construtor de fossas (cloacas). Realizou varias viagens à zona rural da província de Tucumán. Cyclospora cayetanensis é um agente emergente de diarréia e esta é, até onde nós sabemos, a primeira observação de oocistos deste parasito em amostra de vias respiratórias.