A mud that has fewer solids than conventional clay-based muds of the same density and similar use. Low-solids mud design and maintenance is accomplished primarily by substituting one or more polymers for the ordinary bentonite clay. Viscosity can be obtained either entirely by polymers or by using a premium quality (nontreated) bentonite along with the appropriate extender polymer. Together, these give rheology comparable to that of a higher concentration of ordinary bentonite. Polyanionic cellulose (PAC) may be needed for fluid-loss control. XC polymer can be effective for cuttings carrying. By combining premium bentonite and the right extender polymer, PAC and XC polymer, solids can be kept low, if solids control is required. This concept applies best to low-density muds, below about 13 lbm/gal, but has some validity in all muds.