The paper develops on work for the Investment Property Forum study on Liquidity in UK Commercial Property completed by Reading University, Cambridge University and Cass Business School in early 2004. The paper is based on a comprehensive review of transactions activity indicators in the UK market from the mid-1980s to 2002. The transactions evidence is used to track variations in transactions activity over time, and across different market sectors. The descriptive section of the paper answers for the first time questions such as how much transactions activity varies with the cycle, and whether markets in some types or sizes of property are more ëliquidí than others. Analytically, the paper firstly develops models of transactions activity which explain trend and cycle variations in terms of market pricing, the motivations of different actors in the market, and taxes on transactions. Secondly, it tests over time for associations between transactions activity and price behaviour (volatility, serial correlation) of markets both over time and across markets.