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This paper gives an account of an experimental and numerical assessment of the aerodynamic influence of surface imperfections, in the form of sinusoidal waviness, as typically caused by manufacturing malfunctions, on a highly subsonic compressor blade. This knowledge marks a step forward towards an aerodynamically and commercially adequate zero-scrap-rate industrial manufacturing process of expensive integral parts like integrally bladed rotors. The investigation itself used the following approach. First, five potential setups were identified by intensive numerical pre-examination, differing in respect of the two parameters, wave length and wave height. The setups were investigated in the linear cascade wind tunnel of the IST for three operating conditions, with a peak profile Mach number around one, all at constant Reynolds number. It was possible to confirm three main effects responsible for higher losses due to surface waviness. These were: an acceleration on the raising edge of the wave; small shock systems on the first two wave crests; and a shock-induced separation in the wave hollow which leads to a strong shear layer.