Cemented paste backfill (CPB) technology has become widely used in Canada and around the world. While most of the studies related to CPB have concentrated on the mechanical, physical, rheological and economical aspects, very few studies have been conducted on metal leachability. The objective of this study was to investigate the mechanical and environmental behaviour of a novel CPB technique consisting of incorporating various treatment sludges within the conventional paste mixture. For the CPB studied, the binder PC10-50 50/50 offers higher mechanical resistance than the slag-based cement. While PC-based binders are more or less penalized by the addition of sludge, slag-based cement benefits from this additive. In terms of leachability, the results show that PC and slag-based binders were efficient in minimizing the release of Zn and Mn even at a low binder proportion. The addition of 0.15910 and 0.30% of three different sludges to the tailings paste backfill did not have any negative impact on metal leachability. (C) 2005 Elsevier Ltd. All rights reserved.