Pursuant to a congressional request, GAO reviewed the Forest Service's and Bureau of Land Management's (BLM) process for appraising timber offered for sale. GAO found that: (1) BLM and the Forest Service used the transaction evidence appraisal method to advertise timber sales because the method better estimated the timber's fair market value; (2) two of the Forest Service's main timber-producing regions used the residual value method because of limited staff resources and outdated data; (3) Forest Service regions received limited guidance and oversight from headquarters in implementing the appraisal method; (4) regions reduced their appraisal estimates to stimulate competition and compensate for any price inaccuracies; and (5) the Forest Service did t have adequate internal controls over the timber appraisal process. GAO also found that: (1) neither appraisal method ensured a minimum selling price that would adequately protect the government's interest and enhance revenues; and (2) BLM and the Forest Service advertised their fiscal year (FY) 1988 timber sales for less than the costs of preparing and administering the sales.