Pruning provides an important tool for control of nondeterminism in Prolog systems. Current Tabled Prolog systems improve Prolog’s evaluation strategy in several ways, but lack satisfactory support for pruning operations. In this paper we present an extension to the evaluation mechanism of Tabled Prolog to support pruning. This extension builds on the concept of demand to select tables to prune. In particular, we concentrate on systems based on SLG resolution. A once operator is described, which approximates demand-based pruning, providing for an efficient implementation in the XSB system.