Abstract: The present improved bacterial isolation device comprises a bacterial test container with closed bottom, raised sides and open top. A honeycomb type isolation grid providing a plurality of isolated cells is embedded in a layer of non-nutritive medium covering the bottom of the container, so that swarming types of bacteria cannot pass from one isolated cell to another and thus grow over bacteria to other isolated cells and mask them from detection.The improved method and device involve the disposition of a non-nutritive layer in the bottom of the container, covered with a separate layer of selected nutritive medium substantially unmixed therewith and introducing bacteria to the nutritive layer and embedding the isolation grid in the non-nutritive layer, covering the container and incubating the bacteria therein until they can be detected in the isolated grid cells.