Extraction accounts for between 25 per cent, and 75 per cent, of the total costs of production, that is all costs up to roadside ready for despatch, but excluding growing the trees; this percentage, however, depends on the amount of conversion (crosscutting and peeling) and the length and difficulty of the extraction. For this reason, and because extraction is generally more easily mechanised than felling, examination and improvement of extraction methods is likely to be a fruitful way of reducing costs. This publication on extraction is one of a series on work in conifer thinnings; other aspects already described are felling and conversion by hand (Booklet 9); and aids to working (Booklet 8).