The efficacies of different co-disposal strategies (elution, leachate recycle, single addition (batch), single addition plus rain permeation) to treat phenol (1000 and 2000 mg dm(-3)) were investigated with laboratory microcosms. The elution columns recorded the highest total removals but were coincident with low leachate pH values and high residual phenol concentrations. In contrast, leachate recycle facilitated both increased leachate pH values and methane evolution. Rain permeation proved detrimental to phenol attenuation since the molecule was rapidly displaced together with key methanogenic precursors. All the microcosms were characterised by protracted lag phases prior to phenol catabolism and the nitrate- and sulphate-reducing bacteria were particularly sensitive to the added molecule.