To clarify the importance of personal adjustments on office lighting, 17 general office workers and 38 experts in the lighting industry are interviewed. Experiments are conducted to quantify the effect of the subjects' capability to change the illuminance on their satisfaction level, and to distinguish the effect of “control” from the effect of illuminance change itself. It is shown through the interviews that although the awareness on the importance of adjustment is not prevalent, both general office workers and lighting designers regard lighting adjustment as a key factor. Through the experiments, it is observed that evaluations on the lighting environment vary greatly depending on whether or not the subjects are capable of adjusting the lighting level, while effects of both “control” and illuminance change are small.