RESUMO
One hundred and seventy four children from the "República de Checoslovaquia" National School of the Centro Habana-Norte municipality were investigated during the 1976-1977 academic course months. The method of mail interview of parents was used. Every month the history of oropharyngeal infection and antibiotic administration was obtained, and bacteriology of pharyngeal exudates was performed. Antistreptolysin or AELO titers were determined at three-month intervals. Cardiovascular physical examinations were made and electrocardiograms obtained during the last month. 19,22% of exudates were positive for hemolytic streptococci. 46,56% of streptococcal strains isolated corresponded to the group A. Hemolytic streptococci isolation ranged between 10,4% in October, 1976 and 36,1% in April, 1977. The monthly distribution of the different serological groups of isolated hemolytic streptococci disclosed statistically significant differences. 78,26% of the 667 AELO reactions corresponded to titers of 200 or more Todd units. Average titers in the four stages of the serological study are between 382,42 and 463,92 Todd units. Significative differences between the results of bacteriology and serology and the physical state of oropharynx or the history of clinical manifestations were not evidenced. Manifestations of carditis or rheumatic fever were not found.