Poorly regulated landfill disposal is a worldwide problem. This study aimed to assess the risks posed by unsanitary landfill leachates to groundwater quality. The case study presented examines the town of Corlu in the Tekirdag Province of Turkey, where various types of waste are disposed into unsanitary landfill sites without any separation or classification of hazardous and non-hazardous waste. The leachate from unsanitary landfill in Corlu has complex characteristics that are dependent on the composition of solid waste in the landfill. Contamination risks posed to groundwater vary and depend upon the quantity of leachate generated (in this case similar to 13 m(3)/day) and its specific physico-chemical characteristics. Considerable public attention has recently been focused on the environmental and potential human health risks of unsanitary landfill in Corlu. The potential risk of leachate contamination of groundwater resources in Corlu Town is assessed from waste quality, soil characteristics and leachate composition data. General recommendations to facilitate improved future protection of groundwater quality are indicated.