At the start of the Great War pharmacy and the pharmacy profession were as unprepared as everyone else. There was still heavy reliance on drugs of plant origin, and the new chemical drugs were all imported from Germany. Pharmacists shared the patriotic enthusiasm of their countrymen, but the profession had very few female members able to take their places if the men went off to war. But pharmacists were nothing if not inventive, and they quickly adapted to the new situation. This paper explores the role that pharmacy, pharmacists and others involved in making and supplying medicines played in the First World War. It has three main sections; firstly, the Government’s call to arms and how pharmacists responded to it; secondly, the impact of the war on pharmacy on the home front, and particularly the impact on business and the role of women; and thirdly, the role of the pharmaceutical industry, including the development of the gas mask.