The partitioning and transport of myoglobin in cationic, acrylamide-based hydrogels are studied by a microscopic visualization method. Homogeneous cationic gels are synthesized inside fused-silica capillaries with a square section, which allow a direct determination of protein concentration profiles during transient adsorption and desorption. Diffuse, self-similar profiles are observed and used to determine the equilibrium protein binding capacity and the protein diffusivity in the gel. Mass-transfer rates are found to be essentially independent of the external solution concentration, but to vary dramatically with the gel polymer concentration. A Fickian diffusion model with a flux based on the adsorbed-phase concentration gradient is consistent with the experimentally determined concentration profiles for both positive and negative protein concentration steps. The equilibrium and rate parameters determined for the capillary-supported gels also compare favorably with those obtained from macroscopic measurements using composite ion-exchange media comprising similar gels held within the pores of porous silica particles.