The Delphi technique is one method used for combining the knowledge and opinions of a group of experts. The primary characteristic of Delphi is anonymity; correspondece is the communication mode normally used. The concept is based on the premises that opinions of experts are justified as input to decisionmaking where absolute answers are unknown, and a consensus of experts will provide a more accurate response to a question than a single expert. The guidelines presented are for using the Delphi technique to develop habitat Suitability Index (SI) curves. SI curves are often used with the Habitat Evaluation Procedures and are necessary components of the Instream Flow Incremental Methodology. The Delphi technique is not a replacement for scientific methods traditionally used to gather information for SI curve development, but it offers an option that should be considered when SI curves or data for developing needed SI curves are unavailable.