IAU Symposium No. 168, examining the Big Bang and diffuse background radiations, took place on August 23-26, 1994 at the XXIInd IAU General Assembly in the Hague, Netherlands. The meeting attracted a large number - over 250 - of astronomers, reflecting the strong interest engendered by the great advances in cosmology made in recent years. There is still a multitude of unresolved problems in modern cosmology and the symposium offered a wonderful occasion to examine them objectively, at a place where many leading workers in related fields gathered together. After the introduction by IAU President L. Woltjer and the historical background by Vice Present Virginia Trimble, the volume begins with reviews of the cosmic microwave radiation from COBE (Cosmic Background Explorer). Reviews of recent observations then extend from radio to infrared, visible light, ultraviolet, X-rays and gamma-rays. It is followed by theoretical models for the Big Bang and inflation, and alternative views to the Big Bang. Following a discourse on "Probes and Future Tests", the meeting ended with a panel discussion on "Major Unsolved Problems of Cosmology". Contributed papers - both oral and poster reports - are included after the invited talks and panel discussions.