Abstract A novel and simple method is described of preparing a matrix with entrapped antigen, the matrix consisting of well characterized carbohydrates with low toxicity, i.e., dextran and starch, stabilized by crystallization. The crystallized carbohydrate spheres produced probably derive their adjuvant effect from slow antigen release and macrophage stimulation. Five months after a single injection of 80 μg ovalbumin entrapped in dextran spheres, mice produced antibodies against ovalbumin and this response could be enhanced further by co-entrapment of immunomodulators such as DEAE- or SO 4-dextrans into the spheres. A single injection of 8 μg entrapped bee venom into mice gave the same IgG antibody response as 2 × 80 μg bee venom dissolved in water. By the same method it was possible to inject 4 times the LD 50 dose of entrapped bee venom in mice without any significant side reactions.