Lake Lanao is the second largest lake in the Philippines, wholly located within the province of Lanao del Sur. It is of great biological, ecological economic, and social importance – as the seat of evolution of an endemic species flock of cyprinids, as a sizable contributor to the local hydrologic cycle, as the source of water supply riving the Agus hydropower plants, and as the center of life and culture of its native inhabitants – the Maranaos who call themselves the “People of the Lake” (Hansel and Metillo 2016). The first extensive limnological study of Lake Lanao, which is included determination of some of its physical and chemical characteristics, was done by Frey (1969). This was continued by Lewis with his more in-depth field work performed in 1970-71 (Lewis 1973). Frey summarized his morphometric data for Lake Lanao as follows: area – 357 km2; volume – 21.5 km3; maximum depth – 112 m; mean depth (volume/area) – 60.3 m; replacement time (volume/mean annual discharge) – 6.5 years. His other findings showed that during mid-February to mid-March, the lake was essentially isothermal at 24.4 oC, then rapidly warmed to 26.5 oC. During May and June, the surface water warmed to almost 28 oC which was probably the maximum for that year. Lewis (1973) made a more exhaustive study on the occurrence of thermal stratification of Lake Lanao, showing it to be a monimictic lake. Freys additional findings show that dissolved oxygen ranged from 7.3-8.5 ppm at the top 12 m (trophogenic zone) and was slightly supersaturated (106%) from mid-May through mid-June. pH within the top 10 m ranged from 8.2 to 8.9. Methyl-orange alkalinity averaged about 1.2 m.eq. and conductivity about 120 micromhos (1 micromho = 1 microSiemens/cm). The 1% light intensity level varied from 11 to 25 m. Transparency was low during overturn. Since these first studies, various change has occurred. One was affecting the natural variation in the outflow of Lake Lanao, namely the construction of a Marawi Lake Regulation Dam at the mouth of Agus River, effectively making the lake itself its reservoir, which is started operation in 1992. The volume of lake outflow would influence the flushing rate, the rate at which water enters and leaves the lake relative to lake volume, usually expressed as time needed to replaced the lake volume with inflowing water, or its replacement time. Some unusual phenomena have taken place. The occurrence of a fish kill, diagnosed as epizootic ulcerative syndrome by an MSU Team (Escudero et al. 1998) was observed by Lake Lanao fisherman and lakeshore dwellers at around the latter part of December 1997. An unusual greening occurred in September 2006, wherein subsequent to its peak, a hydrobiological investigation of the lake was performed (Lagmay et al. 2006). These unusual occurrences point out the need for a regular periodic monitoring of the lake. Thus, this study sought to measure the current status of various physical and chemical characteristics of Lake Lanao. These include temperature, Secchi disk depth, pH, conductivity, dissolved oxygen, nutrients (nitrate-N, ammonia-N, total phosphorus), alkalinity, and chlorophyll-a, and 5-day biochemical oxygen demand (BOD).