There are few studies on invasive pneumococcal disease in pediatric transplant recipients. Given this fact plus the advent of pneumococcal conjugate vaccines, we conducted a retrospective study at a major pediatric transplant center. The objectives were to determine the incidence and outcomes of invasive pneumococcal diseases in the patient population and to examine the timing of these infections after transplantation. We determined that invasive disease occurred at a rate that was significantly greater than the rate extrapolated from generally healthy children <5 yr of age (176 episodes per 100 000 children per year vs. 35-68.3 per 100 000 children per year). In addition, disease occurred at a median of approximately 20 months after transplantation, thereby theoretically allowing enough time for vaccination with the 7-valent conjugate vaccine. The study also documented significant missed vaccination opportunities.