OBJECTIVE: To study the prevalence of Enterobius vermicularis and its association with finger sucking in young Swedish children. DESIGN: Cross-sectional survey with a questionnaire for symptoms of infestation with Enterobius vermicularis, and the children's habit of finger sucking (including fingernail biting). Perianal tape-test for identification of eggs of Enterobius vermicularis. SETTING: Primary care, day-care centres, and schools in a Swedish middle-sized town (approx. 80,000 inhabitants). PARTICIPANTS: 172 children of both sexes, 4-10 years old. MAIN OUTCOME MEASURES: The prevalence of Enterobius vermicularis and its association with finger sucking. RESULTS: 21% of the children were symptom-free carriers of Enterobius vermicularis, and finger sucking was strongly associated with a positive tape-test (p = 0.01). CONCLUSION: More children than previously known seemed to be symptom-free carriers of Enterobius vermicularis. Finger sucking should be considered when treating infested children and especially those with relapsing symptoms.