The Jandel software "Sigmaplot" 3.0 Windows and the Graphpad software "Prism" 2.0 Windows are well fitting programs even for non-linear regressions. More information about graphpad software is available in the web at http://www.graphpad.com I don´t know, whether Jandel-software is in the net as well. Yours sincerely Dr. R.-A. Vetter