Immobilized biologically active substances comprising microporous, spherical particles in gel form and in the form of a three-dimensional network. These particles contain the biologically active substance entrapped in the meshes of the network. The particles have sizes below 10 .mu.m and the average diameter of the particles is in the range of from 0.5 to 4 .mu.m, preferably 1 .mu.m. The biologically active substance is capable of exerting its biological activity against substances which cannot penetrate into the meshes of the network of the particles. Preferably, the particles are gel grains obtained by copolymerization of acrylic compounds with cross-linkers. The immobilized biologically active substances are used for labelling or separation of cells, cell fragments, viruses or tissue structures having specific receptors or of substances having specific surface structures.