Purpose: To evaluate marginal bone loss on the individual and tooth level, with focus on the importance of the baseline marginal bone level. Materials and Methods: In 1997, 616 randomly selected individuals (mean age 42 years, range 21-63 years) underwent a full-mouth radiographic survey. In 2003, the survey was repeated for 473 of the same individuals (239 females and 234 males). The marginal bone level of each tooth was measured in mm from the cemento-enamel junction to the marginal bone. These measurements were used to calculate marginal bone loss during the 5-year period, and to analyse the average marginal bone loss for the individual, and tooth group in relation to age and to baseline marginal bone level, calculated as the average between measurements in 1997 and 2003 to circumvent regression to the mean. Results: Marginal bone loss rate was on average 0.1 mm per year. For the individual, marginal bone loss was associated with both baseline marginal bone level and age. A significant difference was shown (p 0.05) in marginal bone loss between different age groups, with a stronger association between marginal bone loss and baseline marginal bone level in the youngest age group. Moreover, marginal bone loss differed between tooth groups (p 0.001), with molars and premolars losing marginal bone more rapidly than incisors and canines and showing a stronger association with baseline marginal bone level. Conclusions: Marginal bone loss over a 5-year period is associated with age and baseline marginal bone level. Younger individuals with a reduced marginal bone level were at high risk for further bone loss. Molars and premolars exhibit more rapid marginal bone loss than incisors and canines. Keywords: alveolar bone loss, longitudinal study, radiography