Gianluca,
thank you very much for your Answer. Works like a charm. How come i couldnt find this in the documentation? I did search and browse a lot!
Thomas
You can use ContourPlot3D:
ContourPlot3D[ x^4 + x^5 + z^5 y x \[Minus] y^4 == 0, {x, -1, 1}, {y, -1, 1}, {z, -1, 1}]