Objectives: To explore the impact of contact isolation on the change in functional independence measure (FIM) score, FIM efficiency score, and length of stay. Design: Retrospective matched case control study. Setting: Tertiary care hospital (academic medical center). Participants: Persons admitted to an acute inpatient rehabilitation facility at a tertiary care hospital from July 2009 through December 2010. Methods: Retrospective chart review by obtaining patient data regarding contact isolation status, patient demographics, and rehabilitation diagnosis. Two hundred charts were reviewed, which resulted in identification of 20 patients in contact isolation. These patients subsequently were matched to patients not in contact isolation based on age, rehabilitation diagnosis, and type of insurance. Admission and discharge FIM scores were obtained for these 40 study subjects (20 cases and 20 matched controls). Main Outcome Measurements: The primary study outcome measurements were change in FIM score (discharge FIM score minus admission FIM score), FIM efficiency score (change in FIM score divided by length of stay), and length of stay. Results: Compared with patients not in contact isolation, patients in contact isolation showed no statistically significant difference in FIM score change, a lower FIM efficiency score (. P= .010), and a 39% longer length of stay (. P= .017) when adjusting for confounders. Conclusions: This study identifies contact isolation as a likely variable that is associated with increased length of stay and decreased FIM efficiency score in patients in an acute inpatient rehabilitation facility. Further study is needed to identify the role or mechanisms by which contact isolation is involved in these adverse effects so that interventions may be developed to counteract them.