A new process for the detection of red cell (RBC) antigen antibody reactions is described. It is applicable to most of the tests performed in blood group serology. The procedures are standardized and easy, and they provide clear and stable reactions that improve the interpretation of results. The process uses special microtubes filled with a mixture of gel, buffer, and reagent. Depending on the test to be carried out, the test uses a neutral gel containing no reagents (reagents are added to top of gel) or a specific gel containing reagents (e.g., antiglobulin serum or anti-A, -B, -D, etc.). A suspension of RBCs (for typing or the direct antiglobulin test) or a mixture of RBCs and serum (for reverse ABO typing or antibody characterization) is centrifuged through the gel under precise conditions. In negative reactions, the RBCs pass through the gel and pellet in the bottom of the tube, whereas, in positive reactions, they are trapped in the gel and the reaction may be read for hours afterwards. The test is easy to perform, sensitive, and reproducible. The antiglobulin tests can be performed without washing of the RBCs. There should be a reduction of risk from biohazardous materials.