This guidance is the second revision of Q1A Stability Testing of New Drug Substances and Products, which was first published in September 1994 and revised in August 2001. The purpose of this revision is to harmonize the intermediate storage condition for zones I and II with the long-term condition for zones III and IV recommended in the ICH guidance Q1F Stability Data Package for Registration Applications in Climatic Zones III and IV. The changes made in this second revision are listed in the attachment to this guidance.