High-temperature (200-350degreesC) liquid water (HTW) is a promising reaction medium for conducting acid- and base-catalyzed organic synthesis reactions in an environmentally responsible manner. This article provides a summary of recent advances made concerning acid- and base-catalyzed organic synthesis in HTW. One advance is demonstrating that rates of acid-catalyzed reactions conducted in HTW can be accelerated while maintaining the solvent benignity by using CO2 as an additive. A second advance is showing that additional commercially significant chemical products can be synthesized in HTW without catalyst. A third advance is demonstrating that product selectivity can be controlled by process variables such as temperature, water density, and heat-up time. A fourth advance is the emergence of mechanistic insight regarding acid- and base-catalyzed reactions in HTW. For example, we discuss the possibility that protons or hydroxide ions resulting from the dissociation of water may not be responsible for the occurrence of some classically acid- or base-catalyzed reactions in HTW without catalyst. (C) 2004 Elsevier Ltd. All rights reserved.