SETTING: London, United Kingdom. OBJECTIVE: To explore missed opportunities (MO) for the prevention of tuberculosis (TB) in children aged 0-15 years. DESIGN: Parents/guardians of children aged <15 years diagnosed with TB and reported through surveillance were interviewed about bacille Calmette-Guérin vaccination (MO-V) or contact tracing and screening for TB (MO-C) via an algorithm reflecting eligibility. RESULTS: Annual TB incidence was 12 per 100,000 (65/100,000 in Black Africans, 20/100,000 in Indian or Pakistani children). The response rate was 36% (145/405). About 20% of UK-born children had not been vaccinated. MO-V was not associated with any particular factor. Contact with a known TB case before illness had occurred in 71 children (49%; 71% in those aged 0-1 years vs. 30% in those aged 11-15 years), of whom 64 (91%) were diagnosed through contact tracing. MO-C had been conducted in six (4% overall). Children with MO-C were all of Black ethnic origin. Their index cases were family members (within their household) or relatives or family friends from abroad (outside their household). MO-C was not associated with any other factor. CONCLUSION: Although overall few missed opportunities for prevention had occurred, we recommend increased rigour when performing contact tracing in any case where a child may have been exposed.