The article describes the incorporation of assessment and assurance of learning features in a WWW webfolio system containing student artifacts produced over a fifteen year period by cohorts of students in response to course assignments and program learning objectives. The webfolio system maintains the artifacts; associated assignments; program and course learning objectives; faculty formative comments to students about the artifacts; rubrics; artifact evaluation scores, standards and levels of knowledge along with course information. The data can be maintained indefinitely allowing tracking of trends in assessment results. The relationships among the previously mentioned categories of data as they appear to the users (students, faculty, and administrators) are shown and use of the data to support authentic assessment, assurance of learning, and program improvement is described. Although the data categories are presented in the context of a system built by the authors, similar data would need to be maintained by any system supporting authentic assessment based on student work samples. The paper should be of interest to those involved in using educational technology for assurance of learning and curriculum assessment purpose; those involved in maintaining authentic student work samples for accreditation purposes; and those interested in the use of authentic work samples for professional certification.