The effect of palatal plate therapy on oral dysfunction in children with Down syndrome was studied during a 1-year period. Twenty-nine subjects with a mean age of 24 months were randomized to a test group or to a control group. The variables concerning orofacial muscle function—that is,‘closed mouth’,‘tip of die tongue visible’,‘open mouth’,‘inactive protrusion of the tongue’, and‘active protrusion of die tongue’—were monitored by video recordings. After 12 months of therapy the mean duration of the factor‘closed mouth’was significantly longer (p<0.001) and‘inactive protrusion of the tongue’significantly shorter (p<0.001) in the test group than in the control group. The results indicate that in children with Down syndrome, palatal plate therapy may be a valuable complement to a training program for improving orofacial muscle function.