The recent interest in borate treatment for the production of termite-resistant lumber has led to the need for improved treatment processes. Pre-steaming prior to pressure treatment was known to have a number of potential benefits in terms of improved permeability, moisture distribution and effectiveness of the vacuum. This process was therefore tried on western hemlock dodai (105 mm squares) in an attempt to achieve 80% cross sectional penetration with a minimal diffusion period after pressure treatment. Western hemlock pre-steamed to a core temperature of 82 degrees C in four hours took up almost double the amount of treating solution of end-matched unsteamed samples. There was an improvement in mean heartwood penetration of 45% immediately after treatment and a 134% increase in penetration after one week storage. This was not entirely due to diffusion within the wood but to mass flow of treating solution continuing after the end of the pressure process. After one week storage 64% of samples had 80% of the cross section penetrated. Reducing the vacuum time from 30 minutes to zero had a detrimental effect on penetration. Increasing time under vacuum to 60 minutes provided no beneficial effect. Pre-steaming of hemlock dodai appears to be a very effective means of improving uptake during pressure treatment.