Sapwood of white spruce (Picea glauca) was wounded in the spring with an increment borer.  Tissue adjacent to the wound, collected 4-9 months after injury, was more decay-resistant than uninjured tissue when exposed to Poria monticola or Coriolus versicolor.  No significant quantitative or qualitative differences in lignans were observed between injured and uninjured sapwood.  Injured sapwood contained 30% heptane solubles, compared with approximately 2% for uninjured sapwood or heartwood.  This heptane fraction contained almost entirely resin acids.  Impregnation of decay-susceptible wood of cottonwood (Populus deltoides) with dehydroabietic acid, or with a mixture of resin acids, resulted in a similar increase in decay resistance.