  This paper is concerned with entropy solutions of scalar conservation laws of
the form $\partial_{t}u+\diver f=0$ in $\mathbb{R}^d\times(0,\infty)$. The flux
$f=f(x,u)$ depends explicitly on the spatial variable $x$. Using an extension
of Kruzkov's method, we establish the $L^1$-contraction property of entropy
solutions under minimal regularity assumptions on the flux.
