Alternate assessments are the means through which students with significant cognitive disabilities participate in accountability testing, thus measurement validity of alternate assessments is a critical aspect of state educational accountability systems. When evaluating the validity of assessment systems, it is important to take a broad view of validity that acknowledges its many facets. Evidence regarding six aspects of validity of Utah's Alternate Assessment (UAA) is presented in this paper. These six aspects are: (a) test content, (b) performance standards, (c) administration of the test, (d) reliability of scoring, (e) stability of scores, and (f) impact of use of UAA. Results of the validity study conducted on UAA are presented along with recommendations for improving the system based on these results.