Technical Abstract: Soil aggregate stability is widely recognized as a key indicator of soil quality and rangeland health. However, few standard methods exist for quantifying soil stability in the field. A stability kit is described which can be inexpensively and easily assembled with minimal tools. It permits up to 18 samples to be evaluated in under 10 minutes and eliminates the need for transportation, minimizing damage to soil structure. The kit consists of two 21 x 10.5 x 3.5 cm plastic boxes divided into eighteen 3.5 x 3.5 cm sections, eighteen 2.5 cm diameter sieves with 1.5 mm distance openings and a small spatula used for soil sampling. Soil samples are rated on a scale from 1 to 6 based on a combination of ocular observations of slaking during the first 5 minutes following immersion in distilled water, and the percent remaining on a 1.5 mm sieve after 5 dipping cycles at the end of the 5 minute period. A laboratory comparison yielded a highly significant linear correlation between the stability class and percent aggregate stability based on oven dry weight remaining after treatment using a mechanical sieve. The relationship was not statistically different for a sandy clay loam and a loamy sand. We have applied the method in a wide variety of agricultural and natural ecosystems throughout western North America, including northern Mexico, and have found that it is highly sensitive to differences in management and plant community composition. Although the field kit cannot replace careful laboratory-based measurements of soil aggregate stability, it can clearly provide valuable information when these more intensive procedures are not possible.