Using data from a national study of modern U.S. office buildings, the effects of different lighting designs and glare problems of office workers will be discussed. The study involved 1000 workstations sampled from 13 office buildings. Results for open-plan offices will be presented. These will focus on how factors such as the type of lighting systems and proximity to windows affect workers perceptions of specific lighting attributes and also their perception of overall lighting quality. It will be proposed, among other things that future studies should focus more on measuring the visual quality of the luminous environment rather than simply its lighting qualities.