The objective of this study was to evaluate the effect of weathering on adhesion strength of Scotch pine (Pinus sylvestris L.) samples treated with three concentrations of Tanalith-E. Treated samples were also coated with polyurethane, synthetic and water based varnishes prior to 500 h accelerated weathering test. Adhesion strength between varnishing materials and substrate samples was determined employing pull-off type equipment. Based on the findings in this work adhesion strength values of samples decreased with increasing concentration of treatment chemical. The highest average strength value was found as 3.48 MPa for untreated control samples while 2.88 MPa was the lowest average value for the samples treated with Tanalith-E having 9% concentration and coated with water based varnish. Majority of the failures took place within the adhesion line between coating and the substrate with a very limited torn fibers. Results of statistical analysis revealed that samples coated with three different types of varnishes did not show any significant difference from each other at 95% confidence level. It was also found that chemical treatment of the samples adversely influenced their overall adhesion strength characteristics. (C) 2011 Elsevier B.V. All rights reserved.