This book chronicles the proceedings of the Second Symposium on Particles in Gases and Liquids: Detection, Characterization and Control held as a part of the 20th Annual Fine Particle Society meeting in Boston, August 21-25, 1989. As this second symposium was as successful as the prior one, so we have decided to hold symposia on this topic on a regular (biennial) basis and the third symposium in this series is scheduled to be held at the 22nd Annual Meeting of the Fine Particle Society in San Jose, California, July 29-August 2, 1991. l As pointed out in the Preface to the prior volume in this series that recently there has been tremendous concern about yield losses due to unwanted particles, and these unwelcome particles can originate from a legion of sources, including process gases and liquids. Also all signals indicate that in the future manufacture of sophisticated and sensitive microelectronic components (with shrinking dimensions) and other precision parts, the need for detection, characterization, analysis and control of smaller and smaller particles will be more intensified.