Most particles in nature have irregular shapes. To date, no data have been available for drag force on irregularly or randomly shaped objects; all drag data are for non-spherical objects such as prisms, cylinders, spheroids, etc. that have at least one axis of symmetry. Recently, equations (Johnson, Doctoral dissertation, University of North Carolina, 1985; Johnson et al., J. Aerosol Sci. 18, 87, 1987; Sheaffer, J. Aerosol Sci. 18, 11, 1987; Leith, Aerosol Sci. Technol. 6, 153, 1987) have been developed for drag on non-spherical objects; however, these equations have not been tested on irregular objects. In this work, the drag force on caved prisms, regular agglomerates, and irregular agglomerates was measured to provide data for model evaluations. A new model based on a theoretical equation (Leith, Aerosol Sci. Technol. 6, 153, 1987) and drag data for the agglomerates tested here estimates drag for agglomerates well, adjusted R2 = 0.999, and also works better than published models for drag on a broad set of data for objects with various shapes.