The microbiological cause of peritonsillar abscess and the role of group A β-haemolytic Streptococcus (GAS) are unclear. We performed a retrospective study at the ear, nose and throat clinic (ENT) of Orebro University Hospital, Sweden, and included 376 events of peritonsillitis between 2002 and 2004. We determined if the patients had visited a primary healthcare centre (PHCC) within 30 days prior to inclusion. The results of the rapid antigen detection test for GAS (Strep A) taken at the PHCC were compared with the occurrence of peritonsillar abscess (PTA) and peritonsillar cellulitis (PTC). A Strep A test was performed in 61% (229/376) of the events studied. Strep A was positive in 22% of PTA events and in 35% of PTC events (p = 0.036). Of 48,000 Strep A tests taken in primary healthcare, mainly for sore throat, 22% were positive. We examined the relationship between age, the incidence of PTA, and positive Strep A tests. We also determined if there was a monthly correlation between number of positive Strep A tests and number of PTA events. We found no significant correlations. In conclusion, our findings indicate that GAS does not play a major role in the development of PTA/PTC.