This Workshop, held from January 3-10, 1989 at IMA, focused on the properties of materials which consist of many small particles or grains. These include granular materials, in which the particles interact through direct contact, and suspensions or two phase materials, in which particles interact through the influence of the surrounding viscous fluids. Such materials are important in many industrial and geological applications, especially fluidized beds. This volume contains ad vanced scientific papers in this rapidly developing subject by authors from several different disciplines (e.g., engineering, physics, mathematics). Some papers attempt to derive continuum constitutive behavior from micromechanics. Others analyze theoretically or solve numerically the partial differential equations which result when an ad hoc constitutive law is assumed. Experimental phenomena exhibited by such materials are reported in other papers. Still other consider the application to fluidized beds.