The objective of this course is to familiarize students with isotopic methods that can help improve our understanding of the earth's biogeochemical cycles. Specifically, we will focus on the hydrologic, carbon and nitrogen cycles at local and global scales and on food webs. Initially, we discuss the basic characteristics of isotopic fractionations, notation, and mass spectrometric measurement. The course discussion typically utilizes actual data sets as examples of applying isotopic methodology to biogeochemical problems. The students will learn how to be quantitative with isotopic data through biweekly problem sets. Usually the students have the opportunity to make an oral presentation on a topic of their choice that involves isotopic data.