Aliphatic carboxylic acids (ACA) include many chemicals with a wide range of biological and industrial functions. Many are nutritionally important, occur naturally, and take part in normal biochemical processes. ACA are commercially important with annual production of over 3, 1, and 1 billion lbs/year for acetic, formic, and acrylic acids alone, respectively. Generally, ACA are of no serious concern, except at very high levels of experimental or accidental exposures, many are designated as GRAS. Primary adverse effects are irritation to skin, eyes, and mucous membranes from acute exposures to strong water‐soluble acids that can penetrate the skin or those that can volatilize like short‐chain formic, acetic, and propionic acids; dermal sensitization is rare. Saturated ACA are used in a variety of applications, such as in the production of synthetic fiber, resins, plastics, and dyes. Several acids and their esters are important chemical intermediates or solvents and are used in cosmetics or food applications as pH modifiers, preservatives, and antioxidants. Saturated, straight‐chain monocarboxylic acids are metabolized by the β‐oxidation pathway until acetate, propionate, or butyrate are formed which are utilized for energy production via TCA cycle or converted to acetoacetate and subsequently to other ketone bodies, which can be oxidized or excreted in the urine. Propionate originates from odd‐chain acids and is converted to carbohydrates and, unlike acetate, into lipids. This chapter covers 33 ACA their toxicity and workplace exposure limits under a number of regulatory agencies based on the available data.