Contributions in the past few years on the knowledge of streptococcus, the changes experienced in the pediatric age in its morbility and mortality and modifications in the clinical picture are pointed out. On the base of current knowledge author makes an attempt of classification of streptococcus. Clinical picture, agent, ambient and host are analyzed, with special mention to the patient's age. Signification of streptococcic sensitization and the usual diagnostic error with rheumatic fever are discussed. Finally a brief on mention is made less mentioned streptococcus.