Microscopic examinations were conducted on discoloured hem-fir samples indicating different types of "brownstain" patterns. Distribution of "brownstain" discolouration in hem-fir lumber is variable. Microorganisms were found in all specimens examined. The role of microorganisms in "brownstain" discolourations needs to be elucidated. Research recommendations include monitoring of biological and chemical changes of freshly sawn hem-fir lumber over time.