Laguna de Bay, the largest lake in the Philippines, has a catchment of about 290,000 ha, a surface area of about 90,000 ha, an average depth of 2.8 m and temperatures of 22-34°C, with little or no thermal stratification. Its waters are frequently turbid due to wind-stirred bottom sediments, detritus, inflowing silt-laden streams and dense plankton. It is slightly brackish (< 5%0) during the dry season, when its level falls and waters from the Pasig river and Manila Bay contaming high levels of nutrient wastes enter during high-tide periods. This article describes the fish pen culture in the Laguna de Bay of the Philippines.