Box compression strength and bursting strength of paper intended for the flat and the fluted layers of corrugated board were found to be strongly related to pulp nature, pulp manufacture mode, and paper basis wt. At air humidity > 60%, any strength of corrugated board and box made of it diminished. The paper to be used for flat and fluted layers should contain min. recycled fibers and have a min. basis wt. Temp. and air humidity are crit. on making, stoing and handling corrugated board.