A factorially designed experiment to examine the effectiveness of Ca(OH)2 pre-treatment, enzyme addition and particle size, on the mesophilic (35°C) anaerobic digestion of wheat straw was conducted. Experiments used a 48h pre-treatment with Ca(OH)2 7.4% (w/w), addition of Accellerase®-1500, with four particle sizes of wheat straw (1.25, 2, 3 and 10mm) and three digestion time periods (5, 15 and 30days). By combining particle size reduction and Ca(OH)2 pre-treatment, the average methane potential was increased by 315% (from 48NmL-CH4 g-VS−1 to 202NmL-CH4 g-VS−1) after 5days of anaerobic digestion compared to the control. Enzyme addition or Ca(OH)2 pre-treatment with 3, 2 and 1.25mm particle sizes had 30-day batch yields of between 301 and 335NmL-CH4 g-VS−1. Alkali pre-treatment of 3mm straw was shown to have the most potential as a cost effective pre-treatment and achieved 290NmL-CH4 g-VS−1, after only 15days of digestion.