This recommended practice provides standard procedures for determining the following characteristics of nonaqueous drilling fluids (NADFs): a) drilling fluid density (mud weight); b) viscosity and gel strength; c) filtration; d) nonaqueous fluid (NAF), water, and solids concentrations; e) alkalinity, chloride concentration, and calcium concentration; f) electrical stability (ES); g) lime and calcium concentrations, calcium chloride, and sodium chloride concentrations; h) low-gravity solids and weighting material concentrations; i) sand content; j) high-temperature, high-pressure (HTHP) filtration using the permeability plugging apparatus (PPA)