Children under 24 months of age are at high risk for serious infection with Streptococcus pneumoniae but they do not elicit effective immune responses to the currently available capsular polysaccharide vaccines. A polysaccharide protein conjugated vaccine involving the most frequent types has become an urgent need. To produce such a vaccine for Latin America, information on type distribution is required. Recently, Uruguay was 1 of the 6 countries in Latin America where surveillance for invasive pneumococcal infections in children under the age of 5 years was carried out. Seventy percent of the 182 invasive S. pneumoniae isolates were recovered from patients under 24 months of age, and 19% were recovered from infants under 6 months. The 7 most frequent types were 14, 5, 1, 6B, 3, 7F, and 19A; representing 80% of invasive isolates. Twenty-one types were identified, 16 in pneumonia and 14 in meningitis. Resistance to penicillin increased during the study period, from 29% in 1994, to 40% in 1995-1996, mainly because of the spread of type 14 strains resistant to penicillin and trimethoprim/sulphamethoxazol (89% of resistant isolates). The high proportion of systemic pneumococcal infections recorded in patients under 24 months of age and the increasing resistance of these agents to first-choice antibiotics point to an urgent need for a capsular polysaccharide protein conjugated vaccine.