This book is designed to provide the means of identifying oat varieties so that maximum advantage is obtained from the breeders' efforts by ensuring that the correct variety of grain is planted and delivered. The book is intended for use by those involved at all stages of the oat industry, from breeding and seed production, through growing and harvesting, to receival and segregation, marketing and utilization. Descriptions of the growing plant, panicle and grain are provided to permit identification at any point throughout the life cycle. Despite the biological variation to be expected in the shape and size of a population of grains or panicles of any particular variety, there is still a characteristic uniformity that distinguishes one variety from another. In a sense these differences defy dissection and description, as they are part of an overall impression gained by experience. However, the descriptions and illustrations in this book are provided to draw attention, in a systematic way, to these differences and to provide an aid to the gaining of experience in identification. The term 'variety' is used throughout, because of its general usage, in preference to the scientific word I cultivar.