In a one-year study at the University Hospital of Infectious Diseases in Zagreb, Croatia the rate of asymptomatic throat carriage of beta-haemolytic streptococci was investigated. Throat carriage was investigated in 1796 patients, none of whom had a sore throat nor signs and/or symptoms of a respiratory tract infection. The carrier rate of beta-haemolytic streptococci was 8.3%, for group A streptococci 6%, group B 1.3%, group C 0.3% and group F 0.1%. The highest rate was observed in the 6 to 14 year age group: 13.8% for all streptococcal groups, 11.7% for group A alone. The proportion of non-A streptococci was higher in older age groups. Tonsillectomised individuals were less frequently carriers. No sex or season-dependent variations were observed. In a four-month study of 629 patients with pharyngitis the throat cultures yielded: group A streptococci in 44.7%, group B in 1.7%, group C in 0.8%, and group G in 0.6% of the patients. Group A streptococci in 44.7%, group B in 1.7%, group C in 0.8%, and group G in 0.6% of the patients. Group A streptococcal rates in carriers compared to rates in patients with pharyngitis suggest that approximately one fourth of the schoolchildren with culture-positive pharyngitis actually are not truly infected, but only carriers currently having a sore throat of non-streptococcal etiology. Antibiotics were administrated to 605 (96.2%) patients with pharyngitis; in 571 (94.4%) of the cases before culture results became available. After culture-negative results were obtained the therapy was discontinued in only 28.5% of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)