Microbiologic studies are routinely performed in the assessment of peritonsillar abscess (PTA). Though the bacterial growth rates of PTA are expected to be uniform due to high accessibility and reasonable sterility, they demonstrate a vast range of results, which is partially explained by the differing culturing methods and incubation times. Our aim was to retrospectively examine the changing features identified in the occurrence of PTA bacterial growth rates over a period of seven years. A retrospective study was undertaken on all cases of PTA admitted from January 1996 to December 2002. Details regarding sex, age and country of birth were obtained. Population data and the maximum residue level (MRL) of antibiotics in food were collected. Bacteriologic studies were analysed for gram stain, aerobic and anaerobic culture results, and also antibiotic sensitivities, if obtained. Four hundred and fifty-seven consecutive hospitalisations due to PTA were identified; 281 patients who had 310 hospitalisations with known results of the microbiologic studies were included. The most common pathogens were Streptococcus pyogenes and Prevotella. A statistically significant escalation was seen in the anaerobic growth rate from 6.8% of cases in 1996 to 37% in 1999. A similar change, though not significant, was noticed with the polymicrobial growth rate. None of the parameters investigated showed any statistically significant influence on this tendency. These results may clarify the immense range of bacterial study results reported, suggest a change in the biologic behaviour of the studied bacteria and direct further research.