Streptococcus pneumoniae resistance to penicillin was studied in two hospitals in Caxias do Sul, Rio Grande do Sul, Brazil, between May 1998 and November 2001. From the 176 strains of invasive Streptococcus pneumoniae that were identified, 2.28% (CI 0.62-5.74) presented intermediate resistance, and 3.42% (CI 1.26-7.31) presented high-level resistance. Conclusion was that the use of penicillin in Caxias do Sul was still justified as treatment of pneumococcal pneumonia, differently from other centers where the penicillin was replaced by other antibiotics. These results confirm the statement of IDSA (Infectious Diseases Society of America) guideline for the management of community-acquired pneumonia in adults, that the choice of antimicrobial drug to treat pneumococcal pneumonia should be guided by local or regional prevalence of resistance to penicillin.