Conditions for the gelation k-carrageenan, which is a new polymer for immobilization of enzymes and microbial cells, were investigated in detail. k-Carrageenan was easily induced to gel by contact with metal ions, amines, amino acid derivatives, and water-miscible organic solvents. By using this property of k-carrageenan, the immobilization of enzymes and microbial cells was investigated. Several kinds of enzymes and microbial cells were easily immobilized with high enzyme activities. Immobilized preparations were easily tailor-made to various shape such as cube, bead, and membrane. The obtained immobilized preparations were stable, and columns packed with them were used for continuous enzyme reaction for a long period. Their operational stabilities were enhanced by hardening with glutaraldehyde and hexamethylenediamine.