Two patients with chlamydial pneumonia of infancy are described. One recovered spontaneously without any specific antichlamydial treatment. The other, prior to a belated antimicrobial therapy, developed a persistent and protracted respiratory illness characterized by wheezing. Our observations suggest that: (1) untreated chlamydial pneumonia of infancy may spontaneously resolve, or may become a persistent and protracted disease, and (2) wheezing may be a very prominent manifestation of the disease and should be differentiated from wheezing due to bronchiolitis and bronchial asthma.