The Food and Drug Administration (FDA) is announcing the availability of a guidance entitled "E10 Choice of Control Group and Related Issues in Clinical Trials." The guidance was prepared under the auspices of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). The guidance sets forth general principles that are relevant to all controlled trials and are especially pertinent to the major clinical trials intended to demonstrate drug (including biological drug) efficacy. The guidance describes the principal types of control groups and discusses their appropriateness in particular situations. The guidance is intended to assist sponsors and investigators in the choice of control groups for clinical trials.