“ The limited occurrence of these minerals has resulted in a scant knowledge about their properties in the soils. ” Zelazny and Calhoun (1977) As pointed out by the above authors, the occurrence of natural zeolites in soils is rare and not well known, and only about 75 papers have been published describing the occurrence of zeolites in soils. These occurrences range from hot, humid soils in India to cold, arid soils in the Dry Valleys of Antarctica. Most of these reports describe residual zeolite phases that have persisted from the parent material during soil formation; however, there are reports of zeolites that have formed in soil environments. A variety of natural zeolites have been found in soils, including analcime, chabazite, clinoptilolite, gismondine, laumontite, mordenite, natrolite, phillipsite, and stilbite. Over the past 25 years, natural zeolites have been examined for a variety of agricultural and environmental applications because of their unique cation-exchange, adsorption, and molecular sieving properties and their abundance in near-surface, sedimentary deposits. Natural zeolites have been used as soil conditioners, slow-release fertilizers, carriers for insecticides and herbicides, remediation agents in contaminated soils, and dietary supple-ments in animal nutrition (Ming and Allen, this volume; Pond 1995). These applications can result in direct or indirect incorporation of natural zeolites into soils. If these minerals are to be used effectively in these applications, it will be necessary to understand the long-term stability and effects of zeolites in soils or soil-like systems. Several reviews have been published on the occurrences and properties of zeolites in soils (Zelazny and Calhoun 1977, Ming and Dixon 1987c, Ming and Dixon 1988, Ming and Mumpton 1989, Boettinger and Graham 1995). This chapter provides an overview and update on the occurrence of zeolites in soils and briefly describes methodology used for identifying and characterizing zeolites …