In 1986, the U.S. Environmental Protection Agency (USEPA) recommend two new indicator organisms for recreational water quality assessment. They were enterocci (for both marine and fresh waters) and Escherichia coli (E. coli, for fresh waters only). The two new target organisms required the use of media designed specifically for enumeration of them from ambient waters. Since then, these two media (mE Agar for enterocci and mTEC Agar for E. coli) have been improved, resulting in faster and easier enumeration. The purpose of this manual is to provide specific step-by-step instructions for both the original and the revised test methods (mE, mEI, mTEC, and modified mTEC) used for the new USEPA recommended recreational water quality indicators.