By the method of electrochemical etching the radius development and the transversal etching rate V(perpendicular-to) of single latent heavy ion tracks(Xe-131, 13.02 MeV/u) in thin Makrofol KG foils have been measured at room temperature and controlled 50-degrees-C. The experimental results can be compared with theoretical models about pore growth and ion created damage transversal to the path of the ion. A status report is gi