FDA recently issued a revision of an International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidance document, M3(R2), that was published in 1997 and is intended to harmonize and recommend international standards for non-clinical safety studies conducted to support human clinical trials of a given scope and duration, and/or to be relied upon for marketing authorization for pharmaceuticals. In this revised guidance document, FDA includes a new discussion relating to exploratory clinical studies. Also included are recommendations to help sponsors determine when certain nonclinical studies should be performed, such as phototoxicity studies, immunotoxicity studies, juvenile animal toxicity studies, and abuse potential studies.