A valid and reliable scale for assessing level of sedation would facilitate appropriate sedation management in a porcine intensive care unit (ICU) model. The Richmond Agitation-Sedation Scale (RASS) is used often for human ICU patients. The purpose of this study was to estimate the content validity of the modified RASS for use in sedated, mechanically ventilated swine. The modified RASS includes descriptors specific for swine. A content validity assessment form was developed with 4 items and 5 response choices to assess the modified RASS for relevancy, sufficiency, clarity, and representativeness. The modified RASS and content validity assessment form were emailed to 23 veterinarians with experience in the care of swine or other large animals; participants judged the extent to which the modified RASS is valid for assessing sedation in mechanically ventilated critically ill swine. The criterion for acceptable validity evidence was a content validity index (CVI) of 0.80 or greater. Eight (67%) of 12 veterinarians who responded to the invitation to participate completed the assessment form. The item CVI varied from 0.50 to 0.88; scale CVI was 0.66. Because these values did not meet the a priori criterion, we concluded that the modified RASS does not have sufficient evidence of content validity for use with swine. The reliability of the modified RASS will be tested in the porcine ICU model, and experience with its use in swine will inform refinement of the scale descriptors for repeat assessment of content validity.