The purpose of this study was to compare the onset and severity of gingivitis in children with Down syndrome, when compared to a healthy control group of children. The subjects included 41 children with Down syndrome ages two to 14 years (mean age: 7.6 years) and 112 age-matched healthy controls. We assessed the gingival health of all subjects using the gingival inflammation (M-PMA) index and periodontal probing depth (PD). Children were divided into three age categories: <5 years (AD, 5 to <10 years (AID, and 10 to <17 years (AIII). Supragingival plaque was measured using the Oral Hygiene Index (OHI) and the subjects were screened with the BANA test (Perioscan-Oral-B). Measurement of the M-PMA index in the healthy children showed an age-related increase (F=10.369. p<0.001), and the M-PMA index at the younger age group <5 year (AD was significantly lower than that for the other two age groups AII or AIII (p<0.005, p<0.001). In contrast, the M-PMA index values at AI and AIII in the subjects with Down syndrome were significantly higher than those for healthy children (p<0.001, p<0.001). Both groups had an age-related increase in PD (F=3.388, p<0.05 & F=10.806, p<0.001). and PD at AIII was significantly higher than that at AI in both groups (p<0.01, p<0.001). The children with Down syndrome showed an age-related increase in the BANA test score (F=3.452, p<0.05), and the BANA test score at AIII was significantly higher than that at AI (p<0.02). The BANA test score in the healthy children was not age-related but was significantly higher than that in the children with Down syndrome (p<0.02, p<0.05) .