OBJECTIVES: This study examines long-term prognoses for children with constipation in adulthood and identifies prognostic factors associated with clinical outcomes. METHODS: In a Dutch tertiary hospital, children (5-18 years of age) who were diagnosed as having functional constipation were eligible for inclusion. After a 6-week treatment protocol, prospective follow-up evaluations were conducted at 6 and 12 months and annually thereafter. Good clinical outcomes were defined as > or =3 bowel movements per week for > or =4 weeks, with < or =2 fecal incontinence episodes per month, irrespective of laxative use. RESULTS: A total of 401 children (260 boys; median age: 8 years [interquartile range: 6-9 years]) were included, with a median follow-up period of 11 years (interquartile range: 9-13 years). The dropout rate during follow-up was 15%. Good clinical outcomes were achieved by 80% of patients at 16 years of age. Thereafter, this proportion remained constant at 75%. Poor clinical outcomes at adult age were associated with: older age at onset (odds ratio [OR]: 1.15 [95% confidence interval [CI]: 1.02-1.30]; P = .04), longer delay between onset and first visit to our outpatient clinic (OR: 1.24 [95% CI: 1.10-1.40]; P = .001), and lower defecation frequency at study entry (OR: 0.92 [95% CI: 0.84-1.00]; P = .03). CONCLUSIONS: One-fourth of children with functional constipation continued to experience symptoms at adult age. Certain risk factors for poor clinical outcomes in adulthood were identified. Referral to a specialized clinic should be considered at an early stage for children who are unresponsive to first-line treatment.