Purpose: In an earlier study, the C-CPAR was designed with children, for children, integrating their understanding of physical activity, as well as the content and questionnaire structure they desired. The purpose of this presentation is to discuss the usability evaluation of the Children's Computerized Physical Activity Reporter (C-CPAR) done during a psychometric study comparing a paper-based questionnaire, the C-CPAR, and accelerometry monitoring with 168 middle-school children. The usability evaluation included: (a) the time taken for children to complete the 24-hour self report of physical activity, and (b) the children's perceptions of usability after completing four C-CPAR questionnaires and four paper-based questionnaires over 5-days. Methods: Volunteer participants (N=168) included 7th- 9th graders from an ethnically diverse public middle school in Salt Lake City, Utah. Average age was 13.3 years, with 45% girls (n=76) and 55% boys (n=92) and diverse ethnicity: Caucasian (n=78, 46%), Hispanic (n=67, 40%), African-American (n=9, 5%), and Native American (n=9, 5%), Asian (n=3, 2%), Pacific Islander (n=2, 1%). A four-group randomization was used to control for sequencing of both paper and computer-based questionnaires. The study included: measured height and weight, completion of two 24-hour self-report recalls daily for four days, accelerometry-monitored activity over 5-days, and a 4-item Likert scale usability questionnaire with a section for open-ended comments. Analysis/Results: Overall analysis included hierarchical linear regression modeling (SAS). Usability analysis included descriptive statistics (SPSS), and content analysis (Atlas/ti) of open-ended comments and anecdotal observations by study team. All the children completed the C-CPAR easily, and each wore the Actical accelerometer without difficulty. Average C-CPAR report time was 13.5 minutes for a 24-hour report. Usability evaluation indicated instructions and completion of the questionnaire were easy (95%), the questionnaire included the activities they wanted to report (86%), and time to report was not too long (87%). Qualitative analysis identified several themes, including that the C-CPAR was fun and the lengthy list of activities was well received. The children preferred the computer-based questionnaire to the paper-based questionnaire. Overall, anecdotal comments about the ease of use and activity lists included in the C-CPAR were positive. Of the Spanish-speaking participants, only 15% opted to use the integrated Spanish version. Conclusions: Feasibility and usability of the Actical in middle-school children were demonstrated. Psychometric data analysis is currently in progress. Further evaluation of the C-CPAR in schools and ambulatory care environments will be essential in understanding psychometric base and usability in other venues. Keyword(s): exercise/fitness/physical activity, measurement/evaluation, research