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Effective diffusion coefficients (De) of solutes in immobilized Escherichia coli, Brevibacterium flavum, and Pseudomonas dacunhae cells prepared with polyacrylamide or k-carrageenan gel were determined. A diaphragm diffusion cell which consisted of two compartments divided by a gel plate containing these cells was designed for this work. Ammonium fumarate, ammonium L-aspartate, sodium fumarate, sodium L-malate, L-malic acid, L-alanine, and potassium chloride were used as solutes.Solute concentration, preparative conditions of the gel plate, and temperature influenced the values of De. We found that De values were much smaller than the diffusion coefficients in aqueous solution. A procedure using this diaphragm diffusion cell was velid and favorable in measuring the Dc of solutes in soft materials.