The bacterial growth in patients presenting with a sore throat was assayed and four clinical features were tested in order to reliably differentiate between beta-haemolytic streptococci group A (GABHS) and other micro-organisms. For 2 years, 53 general practitioners (GPs) in The Netherlands took throat swabs from all patients, aged 4–60, presenting with a sore throat lasting 14 days or less. Four clinical features: fever (history), (tonsillary) exudate, anterior cervical lymphadenopathy and absence of cough were registered. In 70% of the 598 patients one or more micro-organisms were cultured from throat specimens. In 48% of the patients beta-haemolytic streptococci were found (32% group A, 7% group C, 4% group G, 5% others). Enterobacteriaceae were cultured in 5%, Candida albicans in 5%, Staphylococcus aureus in 4%, various others in 8% of the patients. In 30% of the patients cultures remained negative. Of the 270 patients with three or four clinical features, 46% (95% Cl, 40–52%) harboured GABHS in their throats, while in 328 patients with less than three features 21% (95% Cl, 16–25%) were GABHS positive. However, this relationship between presence or absence of clinical features and culture result was not found in the youngest age category (4–14 years old). Culture results were not related to sex, smoking habits or the insurance mode of the patient. The clinical relevance of several micro-organisms, other than beta-haemolytic streptococci, remains to be determined. The four mentioned signs and symptoms were helpful in predicting the probability of GABHS in patients aged 15 years and older. More negative cultures were seen in the group with less than three clinical features.