Ceramsite is an inert, heat-resistant, porous material that is made via the calcination of carbonaceous claystone in an oxidizing environment. Its basic mineral constituents are mullite, hematite, quartz, and kaolinite. Ceramsite particles have been proven to be a very practical and convenient bed material for performing various chemical reactions in high-temperature fluidized beds. Experimental measurements Were performed to determine minimum fluidization velocities and the terminal (entrainment) velocities of beds of ceramsite at ambient and superambient temperature. Using air, experiments were conducted in a column with an inner diameter (ID) of 9.4 cm, with very narrow fractions of ceramsite particles spanning a wide range of 0.13-2.25 mm. The minimum fluidizing velocity was determined to decrease as the operating temperature increased for the beds of all the particles, except for the largest ones (2.25 mm). The bed of these particles exhibited an extremal (nonmonotonic) dependence of the minimum fluidizing velocity on temperature. Novel explicit equations have been developed that enable the direct estimation of the particle size corresponding to chosen minimum fluidizing and/or terminal velocities. Those formulas can be applied in engineering considerations and design calculations of fluidizing ceramsite and similar materials.