© 2002 by CRC Press LLC. The purpose of this section is to provide an overview and examples of observational studies; specifically, cohort observational studies that incorporate nutritional assessment. After a brief review of the various types of observational studies and their corresponding purposes, a detailed description of the characteristics, advantages, and disadvantages of a cohort study is provided. Next, in order to demonstrate the use of the cohort design in the area of nutrition, a description of six cohort studies that utilized nutritional assessments is provided. Finally, selected nutrition-related publications from the six cohort examples are referenced, along with the corresponding measured nutritional variables.