Biological and chemical changes were evaluated in freshly sawn amabilis fir and western hemlock lumber (hem-fir) over 10 weeks of outside storage. Both wood species commonly contained brownstain microscopically in heartwood and sapwood. Microorganisms were often found in discoloured samples, but brownstain could not be linked to the presence of microorganisms. Qualitative HPLC analysis was employed on methanol extracted hem-fir segments over time, but this approach provided no indication about potential precursors to hemlock brownstain. However, the HPLC method developed produced a reliable separation and identification of nine wood constituents in hem-fir lumber and can be used for future quantitative analysis. The factors producing macroscopic brownstain were not understood, but a high moisture content appeared to be essential to transport precursors of hemlock brownstain to the wood surface.