Irrespective of the ethnic origin of the patient, nasopharyngeal carcinoma (NPC), appears to stimulate the production of IgA antibodies against VCA. These antibodies are detected at high frequency and titres in sera from NPC patients but only rarely from control subjects. A majority of relapse-free survivors tested 1-12 years after radiotherapy (RT) sustain a detectable level of IgA anti-VCA. Serum titres of IgA anti-VCA remain relatively unchaged in individual NPC patients after RT, regardless of the disease evolution. These antibodies were detected in serum from one individual 9 months before NPC and the titre rose concomitantly with its clinical onset. Titres of IgA anti-VCA in multiple serum specimens from individual NPC patients, and in sera from different NPC patients, do not correlate with titres of IgG anti-VCA or with Serum IgA. It thus seems possible that the IgA anti-VCA in the sera of NPC patients might be largely derived near NPC. Apparently healthy individuals showing detectable IgA anti-VCA tend to aggregate in families of NPC patients. The distribution of siblings of these families who have the IgA anti-VCA reaction shows the binomial distribution expected for an autosomal recessive trait, implying the involvement of an autosomal recessive gene in the IgA anti-VCA response.