  We give a characterisation of factoriality of the groupoid von Neumann
algebra $L(\mathcal{G})$ associated to a discrete measured groupoid
$(\mathcal{G},\mu)$. We introduce the notion of groupoids with `infinite
conjugacy classes' and show that this property together with ergodicity of the
groupoid is equivalent to factoriality of $L(\mathcal{G})$.
