The intention of the Survey of the Nation's Lakes project is to provide a comprehensive State of the Lakes assessment for lakes, ponds, and reservoirs across the United States. This document (Field Operations Manual) contains a brief introduction and procedures to follow at the base location and on-site, including methods for sampling water chemistry (grabs and in situ), phytoplankton, zooplankton, sediment diatoms, pathogens, algal toxins, benthic macroinvertebrates, and physical habitat. These methods are based on both the guidelines developed and followed in the Western Environmental Monitoring and Assessment Program (Peck et al. 2003) and methods employed by several key states that were involved in the planning phase of this project. Methods described in this document are to be used specifically in work relating to the Survey of the Nation's Lakes. All Project Cooperators should follow these guidelines. Mention of trade names or commercial products in this document does not constitute endorsement or recommendation for use. Details on specific methods for site evaluation and sample processing can be found in the appropriate companion document.