Groundwater contamination has been linked to intensive agriculture in many industrialised countries in temperate regions. However, much less research has been done in tropical areas which include some highly intensive forms of farming with significant inputs of fertilisers and pesticides and where rainfall results in leaching for at least some part of the year. The ACIAR project in the Kelantan Plain, Malaysia is the first detailed and systematic study of groundwater contamination in the tropics. A broadscale survey was conducted to determine if the groundwater was contaminated and if so, how widespread it was. The areas studied include high yielding rice production in irrigated areas and also a location where vegetables and tobacco are grown. The initial survey was followed up with more detailed research at representative sites of the rice and tobacco producing areas. These proceedings present the results of that research in papers given at a workshop held in Kota Bharu, Kelantan, Malaysia in October 1994 and include contributions from Australia, Thailand, Indonesia, and the Philippines