In developmental assessment, teachers monitor student progress against a map of developing skills, knowledge, and understanding. Portfolio assessment is a tool to use in developmental assessment, and there are many types of portfolios to support developmental assessment of students. When considering a portfolio type, it is important to consider its purpose and the design elements of content and selection of materials. Three types of portfolios are particularly useful in student assessment and can be used to locate student progress on a progress map. A Working Portfolio is the equivalent of the artist's studio. It shows the work in progress and the tools being used. The best working portfolios become interactive contexts for instruction and feedback. A Documentary Portfolio is a collection of student work assembled specifically for instruction and feedback. It contains final products of student work and evidence of the processes students used to create the work. Show Portfolios are the purposeful selection of a limited amount of the student's best work. Designing portfolios for developmental assessment means paying attention to purpose, content, and selection to illustrate progress in the best way possible. Examples are given of each of these portfolio types, and a summary is provided of the portfolio development process. A number of illustrations highlight specific information about portfolios for assessment.