Details for design and construction of template blocks for the increased sensitivity of radial immunodiffusion (RID) assays are described. The sensitivity of the template RID was 10-fold higher for quantifying albumin and 5-fold higher for IgG than the conventional RID with wells cut into the agarose. The system described in this communication resulted from the unit which provided the most consistent results from a variety of trials with different block thicknesses, chamber sizes and depths, and chamber arrangements.