Updated project metadata. Secretory Carrier-Associated Membrane Proteins (SCAMPs) are highly conserved 32–38 kDa proteins that are involved in membrane trafficking. A proteomics approach was taken to elucidate function of the SCAMPs in wood formation of transgenic Populus trees carrying an RNAi construct for Populus tremula x tremuloides SCAMP3 (PttSCAMP3; Potri.019G104000). Secondary xylem tissues were run on a SynaptTM G2 HDMS mass spectrometer equipped with a nanoflow electrospray ionization interface. Multivariate OnPLS (orthogonal projections to latent structures) modeling was applied to identify consistent changes in the proteomes of the transgenic lines compared to the wild type trees. The woody tissues of the transgenic trees displayed increased amounts of both polysaccharides and lignin oligomers, indicating increased deposition of both the carbohydrate and lignin components of the secondary cell walls. This coincided with slightly increased wood density as well as significantly increased thickness of the suberized cork in the transgenic lines. The OnPLS model identified a rather large number of proteins that were more abundant in the transgenic lines than in the wild type. Several of these were related to secretion and/or endocytosis as well as both primary and secondary cell wall biosynthesis, suggesting function of the Populus SCAMP proteins in membrane trafficking to fine-tune the abundance of cell wall precursors and/or proteins involved in cell wall biosynthesis and transport. The data provides a multi-level source of information for future studies on the function of the SCAMP proteins in plant stem tissues.