okay, solved :-)) It is mentioned here: http://r.789695.n4.nabble.com/How-to-remove-outer-box-from-Wireframe-plots-td824819.html so ... wireframe(z ~ x*y, data = test, scales = list(col = "black", arrows = FALSE), par.settings = list(axis.line = list(col = "transparent"))) ... solves it. Cheers, Marius