It has been suggested that the laccase-mediator system (LMS), an oxidative enzyme system, could be used to delignify kraft pulp. A series of scoping experiments found that this enzyme system could have a range of effects on the physical properties of two high kappa kraft pulps, kappa 70 and kappa 94. The mediator itself (1-hydroxybenzotriazole) was found to modify pulp properties. At a low dose, the mediator alone increased handsheet densification. This effect was negated in both pulps when either a low LMS dose or a high mediator dose was applied. There was, however, an increase in the stretch of the handsheets at a given apparent density that may indicate a change in fiber wall structure. For the kappa 70 pulp, the low LMS dose also increased tensile strength at a given handsheet density. All these changes to the physical properties of pulp, along with changes to optical properties, indicated that a degree of lignin modification had occurred during LMS treatment. Most of the LMS-derived effects were masked by subsequent peroxide extraction. Future work should consider examining the effects of laccase without the mediator.