The plaque control record (O'Leary index) appears to be a commonly used oral hygiene index for assessing oral health skills. This index provides sufficient information for patient education; however, the time involved in data collection reduces its value. Most other indices limit the number of teeth and surfaces and function well for researchers, but are limited for patient education. A new oral hygiene index was developed based on the concepts of the Periodontal Screening and Recording (PSR). The highest score obtained in each buccal and lingual sextant is recorded. In addition, proximal and gingival plaque are noted separately. This study assesses the index for inter- and intrarater reliability and validity. Two calibrated hygienists examined 47 patients 3 times. The University of Mississippi Oral Hygiene Index (UM-OHI) was recorded for times 1 and 3, the O'Leary for time 2. There was a strong positive correlation between scores obtained for both hygienists for each method and repetition. The intrarater reliability was high for the 2 methods and also over time for the UMOHI. Pearson's correlation coefficients ranged from 0.79 to 0.92. Paired τ-tests used to compare scores for the 2 hygienists over time showed significant differences. Despite observer bias, these data seem to indicate that the UM-OHI has sufficient reliability and validity to be used as a health education teaching tool. J Periodontol 1998; 69:1176-1180.