2,394 unaffected individuals from Taiwanese families, in which two or more relatives have been diagnosed with NPC, have been identified and sampled as part of an ongoing collaboration to identify genetic factors linked to NPC development. Serum from these individuals has been tested for three anti-EBV antibodies (VCA IgA, EBNA1 IgA, and anti-DNase) known to be associated with elevated risk of prevalent and incident NPC in general population studies. Results from testing of our study population indicate that apparently healthy individuals from high-risk multiplex families have a near 3-fold elevation in their EBV antibody prevalence when compared to the EBV antibody prevalence observed in the general community for these same EBV markers. However, the clinical implications of this apparent elevation in EBV antibody reactivity are not yet understood.