Kiln drying of radiata pine (Pinus radiata D. Don) sapwood induces a brown discolouration, commonly called kiln brown stain. Kiln brown stain generally occurs 0.5–1.5 mm under the surface of the dry sawn lumber. However, subsequent planing of the wood can expose the stain causing substantial revenue loss in the New Zealand highvalue export markets. In the present study, the effects of kiln schedule temperature, wood moisture content and kiln relative humidity on kiln brown stain formation were investigated. The results showed that kiln brown stain was greatly reduced by using kiln schedules of less than 50°C as opposed to 90°C and was also more pronounced in the kilning at 30% kiln relative humidity, than at 80% humidity. Furthermore, the occurrence of kiln brown stain tended to intensify with decreasing wood moisture content, irrespective of kiln temperature and kiln humidity used. The practical implication of this work and the mechanisms of kiln brown stain formation are discussed.