This is the first time that the International Astronomical Union has held a symposium on objects of totally unknown nature. In fact. M. Rees has pointed out that the mass of the individual particles that make up the dark matter is unknown to > 70 orders of magnitude. Since dark matter appears to make up ~ 90 % of the mass of the Universe. it presents us with one of the most fundamental problems in astrophysics. IAU Symposium 117 on Dark Matter in the Universe was held on June 24 - 28. 1985. Our hosts were Princeton University and the Institute for Advanced Study. which together form one of...