Stool examination was performed on 2,083 Thai children from orphanages and primary schools. Hymenolepis nana infection was found only in children from orphanages with a prevalence of 13.12 per cent. Males had a statistically significant higher prevalence of infection than females. Most infected children were asymptomatic. In symptomatic infected children, the symptoms were mild and non-specific such as pruritus ani, abdominal pain, diarrhea, anorexia, headache, and dizziness. Praziquantel in a single oral dose of 25 mg/kg body weight was effective and well tolerated in Hymenolepis nana infected Thai children.