The present investigation was designed to determine the individual variation of plaque levels in adults over a period of 3 months. The participants were 20 healthy subjects, 11 men and 9 women, with a mean age of 42.3 +/- 7.3(SD) years. Plaque area was determined with a computerized image analysis system and expressed as percentage of tooth area (P% Index). The scoring procedures were carried out three times (tests 1, 2, and 3) at an interval of 4 weeks. After each test all plaque was removed. All subjects were instructed to maintain their personal oral hygiene habits during the study. The results showed no significant differences for the means of P% Index between tests 1, 2, and 3 in the whole mouth, upper and lower jaws, right and left sides, or each tooth surface. The intraindividual plaque levels for individual tooth surfaces were closely correlated between tests 1, 2 and 3. The intraindividual plaque level was consistent in tests 1, 2, and 3 with standard deviations within subjects ranging from 1.1% to 6.2%. This study suggests that individual plaque levels seem to be consistent on the basis of tooth surface over a certain period of time. Individual plaque control should be more directed towards tooth surfaces with comparably high plaque accumulation within the mouth for significant reduction of the overall plaque levels.