This symposium has brought back many happy memories of the time 20 years ago when Rashid Sunyaev and I surveyed what was known about the extragalactic background radiation at that time. In one of our papers of 1969, we published a simple representation of the extragalactic background radiation spectrum, as it was known then (Figure 1). Extragalactic background radiation had been discovered in the radio, microwave, X- and γ-ray wavebands but only upper limits were available in the intervening wavebands which have been the principal concern of this symposium. It is remarkable that, over the last 20 years, although the observational techniques have developed dramatically and there have been enormous astrophysical advances, the wavebands between 1 mm and 1 nm have continued to be very difficult indeed for studies of the extragalactic background.

The most striking aspect of this conference with respect to galactic studies has been the confrontation between wavelengths. The study of the background radiation requires absolute measurements of low brightness over very extended regions. Such measurements are known to be extremely difficult. We now can confront data on the galactic background at all frequencies. The data from far ultraviolet to submillimeter give particularly useful constraints on both the direct interpretation of the data and on their astrophysical interpretation.