Adjuvant research has improved the ability of biotechnology to generate novel vaccines. Numerous strategies for enhancing the immunogenicity of synthetic peptides and proteins have been identified. This overview focuses on adjuvant development and vaccine delivery systems that provide new tools for amplifying the effectiveness of ongoing malaria and AIDS vaccine development programs. In addition, some of the complex challenges and issues that have become associated with the delivery of modern vaccines in man are outlined. As adjuvant research continues to open new opportunities in vaccine development, there is renewed expectation that further generations of safe and potent vaccines will be possible against a broad spectrum of infectious agents and cancer.