In a 3-week-old baby with lung infiltrate Streptomyces pelletieri was cultured from lung exudate obtained by percutaneous needle aspiration. The same organism was found in the mother's vaginal discharge. Transmission of the organism from mother to baby at birth is most probable. Treatment with penicillin and sulfonamides in both mother and child was effective. Human infections with S pelletieri have hitherto not been described in Europe.