\documentclass[a4paper]{article}

\usepackage{pgfplots}

\pgfplotsset{compat=1.3}

\begin{document}

\begin{tikzpicture}
	\begin{axis}[colorbar,title=xzy]
	\addplot3[contour gnuplot={axes={x}{z}{y}}] {x^2-y^2};
	\end{axis}
\end{tikzpicture}

\end{document}

