The demands for sustainably produced wood as a raw material for a variety of end uses is placing increased pressure on the forest resource in the UK. Knowledge of the timber properties of trees and logs is important to ensure that harvested wood is directed to its most appropriate end use. Current harvesting practice in the UK means that trees are often felled, processed and dried before the timber is strength graded by machines at the sawmill. This process can be inefficient if timber destined for structural uses is later found to be unsuitable; downgrading may incur significant financial and environmental costs. The use of acoustic technology to predict the mechanical properties of timber is a well-established practice overseas. Recent advances in technology and the development of portable instruments mean that wood can now be assessed in standing trees before they are felled. Trials in the UK have shown that it is possible to relate measurements of acoustic velocity in standing trees and logs to the mechanical properties of timber cut from them. This gives the potential to segregate material for different end uses in the forest, at the roadside or in the sawmill.