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The aim of this work was to study and compare macrolide resistance patterns among Streptococcus pneumoniae, Streptococcus agalactiae and Streptococcus pyogenes, to describe the phenotypes of macrolide-lincosamide resistance and to further investigate associations between macrolide resistance and social clustering. Susceptibility data were obtained from 4 clinical microbiology laboratories in Bariloche, Argentina for the period 2002- 2008. Patients were differentiated in two population clusters according to the institution they attended (public or private). A total of 4310 strains were studied: 2615 S. pyogenes, 995 S. agalactiae and 700 isolates of S.pneumoniae. Erythromycin resistance rates over the study period were 1.5% for S. pyogenes, 7.8% for S. agalactiae and 11.3% for S. pneumoniae. For the complete study group, these values differed significantly among species (contingency table  2 = 164.52, p