At the beginning of the 1990s, the prevalence of penicillin resistance of Streptococcus pneumoniae strains in Hungary was found to be extremely high (up to 58% non-susceptible) in some studies, while in other publications the percentage of penicillin highly resistant strains was 0-2%. To see whether this was due to differences in methodology or the composition of the patient population studied, a retrospective evaluation was carried out of the penicillin, amoxicillin, ceftriaxone and macrolide resistance of all S. pneumoniae strains isolated from in- and outpatients in our laboratory between 1998 and 2005. Of the 2670 S. pneumoniae isolates only 5.58% was found to exhibit high-level resistance to penicillin, while resistance to amoxicillin, ceftriaxone and erythromycin was 2.62%, 1.12% and 42.06%, respectively. During this period 6 (3.8%) of 155 S. pneumoniae strains isolated from invasive samples displayed high-level resistance to penicillin. Earlier surveillance data on penicillin resistance of S. pneumoniae may have been biased by the age groups affected by the infection, by whether the strain was isolated from an out-patient or an in-patient, and by whether the isolates were obtained from invasive samples. Our 8-year study using the NCCLS/CLSI methodology consequently revealed a low prevalence of high-level resistance to penicillin in S. pneumoniae strains obtained both from adults and children.