A monolithic wide-pore silica column was newly prepared for protein separation. The wide distribution of the pore sizes of monolithic columns was evaluated by mercury porosimetry. This column, as well as the conventional monolithic column, shows high permeability in the chromatographic separation of low-molecular-sized substances. In higher-molecular-sized protein separation, the wide-pore monolithic silica column shows better performance than that of the conventional monolithic column. Under optimized conditions, five different proteins--ribonuclease A, albumin, aldolase, catalase, and ferritin--were baseline-separated within 3 min, which is faster than that using the particle-packed columns. In addition, the monolithic wide-pore silica column could also be prepared in fused silica capillary (600 mm long, 0.2 mm i.d.) for highly efficient protein separation. The peak capacity of the wide-pore monolithic silica capillary column is estimated to be approximately 300 in the case of protein separation, which is a characteristic performance.