Abstract: A roof transition flshing (10) for installation to a building at a juncture between a vertical wall (40) and an edge (46) of a sloped roof (44), to prevent water flowing along the flashing (10) from seeping behind siding (42) located on the vertical wall (40) and shingles (48) located on the sloped roof (44). The roof transition flashing (10) comprises an L-shaped member having a vertical planar section (16) and a transverse planar section (18). The transverse planar section (18) extends generally laterally from the vertical planar section (16) and is joined thereto by a first imperforate seam (20). The vertical planar section (16) is positioned under the siding (42) and flush with the vertical wall (40) and the transverse planar section (18) is positioned under the shingles (48) and flush with the sloped roof (44). The L-shaped member has an upper end (14) and a relatively lower end (12).