Objectives: To discuss the development, use, and validity of the actual reality tasks and scoring system in persons with multiple sclerosis (MS). Design: Measurement development; cross-sectional correlational study of neuropsychologic and functional actual reality task performance. Setting: Neuropsychology research laboratory. Of note, the actual reality task can be performed anywhere as an Internet-based task. Participants: Persons in the community with relapsing-remitting MS and age- and education-matched healthy controls between 20 and 60 years. Interventions: Not applicable. Main Outcome Measures: Actual reality scores and the MAC-FIMS (a neuropsychologic assessment battery sensitive for use in persons with MS). Interrater reliability for actual reality scoring is also reported. Results: Persons in the MS group committed significantly more errors on the actual reality task than healthy controls. Interrater reliability for the actual reality scoring system is very high (>.90) for scoring errors and classifying cognitive capacity scores, respectively. There were significant correlations between the actual reality task and measures of processing speed, working memory, and verbal learning and memory. Conclusions: Actual reality and its scoring system have support as a valid and sensitive functional assessment approach in persons with MS.