SummaryData have been presented which illustrate the detergency properties of soap‐sodium carboxymethyl cellulose‐builder systems. Practical considerations limit use of CMC to the lower concentrations, and it has been shown that at sodium carboxymethyl cellulose concentrations of 5%, or even less, builder tolerance is increased without sacrifice in soil removal properties. At CMC concentrations above 3% the soil removal properties of the ternary systems under study are increased above that of soap alone except in the case of very high builder content. Within common soap: builder ratios the whiteness retention properties of the system are substantially increased by the addition of CMC. Both soil removal and whiteness retention properties of unbuilt soap are also increased by the addition of small amounts of CMC.