A description of an extensive investigation of the preservative treatment of structural timber using five water-born and five oil-type preservatives. Timbers were treated by dipping, and the uptake of preservative and rate and depth of penetration were measured. The investigations included dependence of uptake on wood species (spruce, fir and pine); the effect of m.c. and temperature and time of impregnation on the uptake; and the increase in uptake achieved by perforation of the wood surface. -- AATA