Swirl defects in p-type Si wafers are studied by Makyoh topography (MT). Two series of wafers of varying dopant concentration are compared. The unambiguous correlation with the high dopant concentration is shown, and the differences between the wafers of the two vendors are pointed out. The results are interpreted using a geometrical optical model of MT imaging, and arc compared to surface Stylus measurements. The possibility and limitations of the extraction of quantitative data are discussed. Other defects are also observed and the possible origins are discussed. (C) 2008 Elsevier B.V. All rights reserved.