Objectives: To compare periodontal health of Polish 12-year-olds in 1987, 1995 and 2003. Methods: The nation wide survey covered 1380 children in 1987, 1859 in 1995 and 3338 in 2003. Children were chosen by stratified random sampling and examined in schools by calibrated epidemiologists using WHO probes under artificial lighting. The presence of dental calculus and bleeding on probing were recorded. Results: The percentage of children with a healthy periodontium increased from 24.0% in 1987 to 24.7% in 1995 and 61.8% in 2003. At all time points, the percentage of children with a healthy periodontium was higher in children from urban than from rural environments, and was slightly higher in girls than in boys. The mean number of healthy sextants (CPI=0) in 2003 was 4.52, and varied from 2.16 to 5.81, depending on the region. A total of 13.3% at this time point had no healthy sextants. This varied from 0.0% to 59.3%, depending on the region. The proportion of children with no healthy sextants was higher in children from rural areas (16.0%) than urban areas (10.8%), and in boys (15.5%) than girls (11.1%). The percentage of children with bleeding on probing decreased from 55.0% in 1987 and 55.7% in 1995 to 30.5% in 2003, and the percentage of children with dental calculus decreased from 21.0% in 1987 to 19.6% in 1995 and 7.6% in 2003. Conclusions: Results showed a marked improvement in periodontal health among Polish 12-year-olds between 1987 and 2003. This improvement was most evident within the last 8 years, during which the percentage of children with a healthy periodontium more than doubled. The introduction of wide-scale school-based oral health promotion for primary school children in 1993/1994 may have been a factor contributing to the marked improvement in parameters of periodontal health during this time period.