The bulletin explains causes of undesirable flavors in milk, cream, butter, and cheese, grouping faults into three origins: volatile compounds from feed or the animal, odors absorbed from unsanitary surroundings, and changes produced by bacteria, molds, and yeasts. It outlines how temperature and time favor microbial development, how some butter and cheese flavors result from bacterial or enzymatic decomposition, and how aeration, prompt cooling, clean utensils, and careful feeding reduce taints. Practical investigations are described, including tracing a persistent fishy smell to an individual animal, illustrating diagnostic and remedial measures for dairymen and processors.