AbstractIn recent decades, soap has largely been replaced by petrochemicals and polyphosphates as the major components of laundry detergents in the U.S. Currently, the use of soap is primarily confined to the toilet soap bar field, and technological advances here have been mainly in processing. In view of the rising costs and increasing scarcity of petrochemicals and polyphosphates, tallow, a replenishable, inexpensive agricultural by‐product, was examined as an alternate raw material. Tallow soap has a long history of efficacy and safety but suffers from poor performance in hard water and insolubility in cold water. It has now been shown that the performance of soaps can be drastically improved in cold water solubility and in hard water detergency by the addition to the soap of lime soap dispersing agents (LSD A). These are anionic or amphoteric surfactants possessing one or more bulky polar groups. These soap‐LSDA combinations form mixed micelles in water and essentially take on the surface active characteristics of a single anionic surfactant. Soap‐LSDA combinations wash well in hard water without curd formation; they can be “built” with various materials such as phosphates and trisodium nitrilotriacetate (NTA) to enhance detergency. Soap‐LSDA combinations equal the conventional detergents in every performance respect and undergo biodegradation more readily and completely.