Technical Abstract: It has become apparent that microorganisms are distributed in the environment in an extremely patchy manner and that the patch sizes are quite variable in magnitude. In terrestrial systems, patchiness appears to generally increase with depth. Neither the factors that control these distributions nor the distributions themselves have been rigorously quantified. To quantify relationships between microbial spatial distributions and their controlling factors, the relevant scales and most probable controlling factors need to be identified. To that end, published data on subsurface microbial properties from spatially arranged sample sets are reviewed and used to construct and support conceptual models of microbial distributions in terrestrial subsurface environments.