This volume contains contributions based on the lectures delivered at the Fifth International Symposium on Quantum Optics. This Conference, the fifth in a tri­ ennial series hosted in New Zealand, was held in Rotorua, 13-17 February 1989. The Conference was attended by 75 participants from New Zealand, Australia, Japan, USA, France, Italy and Germany. There was also a high level of par­ ticipation from graduate students from New Zealand and Australia, who greatly benefitted from the opportunity to attend world-class conferences. The partici­ pants were housed in the Hyatt Hotel and surrounding motels and all enjoyed the relaxed atmosphere offered by Rotorua in the Southern Hemisphere summer. There were 24 invited papers, given as oral presentations of 40 minutes, and 22 poster papers. The major topics covered at the Conference were new experimental and theoretical results in nonclassical light, including sub-shot-noise light sources. We were fortunate in that all major experimental groups in the world working in this area were represented. The latest experimental results from AT & T Lab­ oratories, NT & T Laboratories, mM Laboratories, Ecole Normale Superieure and the Californian Institute of Technology were reported. New theoretical results from Southern Hemisphere participants included a true phase operator for quantum fields derived by Professor David Pegg of Griffiths University and a general treatment of lasers pumped without shot noise by Professor D. F. Walls of Auckland University.