Museums must choose illumination that will optimize observers' aesthetic experiences without compromising preservation of the artworks. Typical lighting is 3000 K at 200 lux. We examined the effects of color temperature by comparing the same "artwork" under several different illuminants (in side-by-side miniature museum rooms); for each painting, observers rated the preference for seeing it under one of the two illuminants; this was repeated for all pairings of illuminants. Our observers preferred higher color temperatures at about 3600 K. Between viewing trials observers' visual systems were adapted to a specific illuminant. This had no effect on preferred illumination of an artwork. To explore a wider range of artworks, we developed a set of numerical scales that could be applied directly to individual pictures; these were viewed, one at a time, in a single simulated room illuminated by one of a series of illuminants. Again, observers preferred a color temperature of about 3600 K. In both studies there was a small interaction between illuminant and color gamut of a given painting. (C) 2004 Wiley Periodicals, Inc.