Historical introduction to treatment of waterlogged wood presents early recipe for alum (1861), the use of which continued for roughly 100 years. This treatment did not prevent shrinkage; treated wood was heavy, brittle, and hard. Boiling alum is a safety hazard. An alum/glycerol solution developed in 1934 presented its own set of problems. Polyethylene glycol (PEG) (Carbowax or polyoxyethylene) was first manufactured in the late 1940s, but not used until the 1960s; problems with its use are discussed. Work on the <i>Wasa</i> is compared with treatments of Danish Viking ships at the National Museum of Denmark. A t-butyl alcohol exchange with water, PEG 4000 impregnation, and vacuum freeze-drying appears to be more satisfactory than other treatments have been. The acetone-rosin method involves dehydrating wood with acetone and then application of rosin or colophony to penetrate wood. Rosin tends to oxidize, and the wood so treated becomes brittle; thus far, no aging studies have been performed on wood treated in this manner. The Arigal treatment has been used on Swiss Lake settlement material; its drawback is that it is not reversible. Diethyl ether has a low flash point; thus its use in the alcohol-ether-dammar resin method poses a safety hazard. Comparison tests are reported, but these failed to take into consideration improvements in freeze-drying techniques developed at the Canadian Conservation Institute. Cellulose's role in deterioration is discussed; a formula has been developed to determine the appropriate solution of PEG to fill the secondary space, to penetrate the cell wall; this formula is given as well as a computer program to perform the calculation. Ten criteria are listed for selecting a particular method of treatment. -- AATA