Anomalous peaks in the resistivity profiles of p-on-p+ epi wafers as measured using spreading resistance analysis have been observed. The fact that these peaks have similar character and are observed on epi wafers from different sources makes it improbable that they are caused by compensating contaminants. Simulations of the spreading resistance profiles of such wafers are described which show that the anomalous peaks may be explained by the combined effects of charge near the surface and analysis by multilayer theory (the standard method for analyzing spreading resistance profiles). © 1990, The Electrochemical Society, Inc. All rights reserved.