This article discusses how to develop portfolios in physics in order to assess student attainment of course goals. Portfolio assessment can include many forms of alternative assessment. Portfolios require students to collect and reflect on examples of their work. This form of assessment forces alternative ways of thinking by the teacher about what is done and what is measured. Portfolios also provide an important intersection of instruction and assessment. A portfolio should contain evidence of what a student knows and is able to do. The evidence must have two parts. The first part is the documentation. Documents may be of any nature that the student chooses. Along with the documentation, students must provide a caption. The caption allows students to describe their learning and growth in the course. Students should also have the scoring guide when developing their portfolios. Students should be aware of what is required to develop documentation to meet the goals described. With portfolios, students can demonstrate that they not only have mastered the facts about natural events, but also have constructed knowledge that represents the concepts and processes of science and captures the excitement of the scientific enterprise. (Contains 3 figures.)