The aim of our study was to compare the changes in children's oral health-related behavior, knowledge, and attitudes obtained using an oral health-promotion approach, a risk-strategy and promotion approach, and reference area, and to report changes in the behavior of children between the experimental and the control groups of a randomized clinical trial (RCT). The study population consisted of all fifth and sixth graders who started the 2001-2002 school year in Pori, Finland (n = 1,691), where the RCT and program of oral health promotion were implemented for 3.4 yr. Children with at least one active caries lesion were randomly assigned to experimental (n = 250) and control (n = 247) groups. Children in Rauma (n = 807) acted as the reference. Changes in children's self-reported behavior, knowledge, and attitudes were compared between groups. The subjects in the oral health-promotion group and in the risk-strategy and promotion group in Pori tended to show greater improvement in most of their oral health-related behaviors than those in the reference group, and children in the RCT experimental group showed greater improvement in most of their oral health-related behaviors than those in the RCT control group. Children can be helped to improve their oral health-related behavior by intervention, including oral hygiene and dietary counseling, or by implementing a multilevel-approach oral health-promotion program.