Human immunodeficiency virus (HIV) has infected 50 million people worldwide and killed 16 million so far, and the epidemic is still spreading with 16,000 new cases of HIV infection daily and a projection of 100 million infected individuals by the end of the next decade. There is no question that a safe and effective acquired immunodeficiency syndrome (AIDS) vaccine is urgently needed to bring the current AIDS pandemic under control. But, is preventive AIDS vaccine an attainable goal? Unfortunately, the results of many laboratory and clinical studies over the past two decades are not encouraging. We comment on the efficacy, safety and ethics of AIDS vaccine, and the urgent need for a new strategy for AIDS vaccine development.