Conjugate vaccines have already had a major impact on vaccination of infants against H. influenzae type b. The impact of conjugate vaccines will continue to grow as we apply this technology to other important diseases. The design of these vaccines will become more efficient and rational as we continue to understand the various facets and immunological mechanisms important to the function of conjugates. This understanding will lead to development of new and innovative approaches to using conjugate vaccine technology. Several new and important conjugate vaccines are already in clinical trials. We look forward to the future wide-spread use of these and other future conjugate vaccines.