Introduction: This study investigated differential item functioning (DIF) of test items on Pennsylvania's Alternate System of Assessment (PASA) for students with visual impairments and severe cognitive disabilities and what the reasons for the differences may be. Methods: The Wilcoxon signed ranks test was used to analyze differences in the scores of the students with visual impairments and severe cognitive disabilities who took the Grade 3-4 or 7-8 Level A PASA compared to matched peers without visual impairments. The students with visual impairments were analyzed as a group and by level of functional vision. Logical analyses of videotaped assessments of the students with visual impairments were conducted to identify potential sources of DIF. Results: Among the functional vision groups, 17 instances in reading and 22 instances in math were flagged for DIF, with 14 skills in reading and 13 in math emerging as harder for students with visual impairments. The types of items that were significantly different included those involving money, matching, and selecting the smallest. Potential reasons for the differences included students needing a better orientation to test materials; the influence of lucky guesses based on distractor characteristics; and the influence of accommodations, such as the substitution of objects. Discussion: The results demonstrate the complexity and importance of evaluating the validity of alternate performance-based assessments for students with visual impairments and severe cognitive disabilities. The themes that emerged suggest the need to structure alternate assessment tasks for consistent orientation to materials and to consider closely how accommodations affect the difficulty of the tasks. Implications for practitioners: Practitioners should consider how the reading progression for their students with visual impairments and severe cognitive disabilities is related to alternate standards and the instruction that is in place to learn concepts that were missed incidentally. Practitioners can help improve alternate assessments by communicating with their states about the types of tasks that are difficult to accommodate in their current format or by requesting guidance in making meaningful accommodations that maintain the intent of the items. (Contains 3 tables and 1 box.)