Wastewater is the term for discarded or previously used water from a municipality or industry. The wastewater that is produced due to human activities in households is called domestic wastewater i.e. wastewater from the kitchen, bathroom, toilet and laundry. Such water usually contains dissolved as well as suspended matter and must be treated prior to its discharge into natural water. To examine the quality of wastewater to be discharged into aquatic Environment or to be treated and reused, the characteristics of wastewater in question must be defined precisely. Quantitative assessments of the quality of wastewater are made by considering many criteria, including temperature, dissolved oxygen level and concentration of organic as well as inorganic compounds. The most frequently used parameters are: Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), Alkalinity, Chlorides, Nitrogen, Oil and Grease, Dissolved Oxygen, pH, Phosphorus, Gases, Sulphur, Solids, Temperature, Metals as well as Micro-organisms. In this lesson, these parameters are defined and methods for analysing them are discussed briefly. In addition sampling and determination techniques are discussed.