The acquired immunodeficiency syndrome (AIDS) epidemic has focused increased attention on new drug development and the Food and Drug Administration (FDA) evaluation process for durgs to treat patients with AIDS and other severely debilitating or life-threatening illnesses. To expedite the review of these experimental drugs and to make them available to patients earlier in the development process, the FDA has implemented new procedures and mechanisms. In the new drug regulations, the subpart E procedures commit the FDA to extensive and intensive participation in the initial stages of development of these drugs. Early consultation by the FDA with drug sponsors, more frequent meetings between the FDA and drug sponsors, larger and more extensive phase 1 and phase 2 trials, and postmarketing surveillance are some of the key features of these FDA procedures. The subpart E procedures reflect the philosophy that early involvement by the FDA in drug study design enhances the likelihood that the results from these studies will provide enough information to allow the FDA to more quickly assess the safety and efficacy of these drugs. Treatment Investigational New Drug Applications (INDs) increase the early availability of experimental drugs in the final stages of the FDA evaluation process, but before final approval. Both the parallel track proposal and the accelerated drug approval concept are additional mechanisms intended to increase the early availability of drugs for patients with AIDS. This is a US government work. There are no restrictions on its use.