This article documents a feasibility study on coating fine powders with protein solutions using a Wurster spray coater (GPCG-1 from Glatt Air Techniques, Ramsey, NJ). Spray coating was based on a fluid-bed process where fluidized microcarriers were coated inside the Wurster column and dried in the fluidization chamber. Recombinant human deoxyribonuctease (rhDNase) was used as the model protein. Lactose powders of two different size ranges, 53-125 and 125-250 pm, were used as the model microcarrier. The am ou nt of protein applied was varied to obtain coatings of varying thickness. The extent of rhDNase loading determined experimentally was found to be consistent with the theoretical value and was also confirmed visually by scanning electron microscopy. The coating showed a strong integrity after being subjected to mechanical force. However, the protein suffered serious aggregation during coating, most likely due to the thermal stress of the process. Aggregation was significantly reduced when rhDNase was formulated with calcium ions, consistent with the observation that Ca2+ thermally stabilized the protein (as determined by scanning microcalorimetry) in aqueous solution. Thus, our study demonstrates that spray coating, particularly when used in conjunction with rational stabilization strategies, is a feasible alternative to other methods of preparing dried pharmaceutical proteins.