A study of nasopharyngeal carcinoma (NPC) families with two or more affected members was conducted in Taiwan (265 families with 2,444 individuals, 502 affected and 1,942 unaffected) to determine the association between NPC and potential etiologic factors in NPC high-risk families. Similar to results from a previous case-control study in Taiwan, Guangdong salted fish consumption during childhood, exposure to wood, and betel nut consumption were all associated with elevated NPC risk using conditional logistic regression, although these associations were not as strong as in the case-control study possibly due to shared environment among family members. Risk associated with cumulative wood exposure and salted fish consumption before age 10 was stronger in families with early NPC age-onset [odds ratio (OR(wood)), 5.10; 95% confidence interval (95% CI), 1.50-17.34; OR(fish), 3.94; 95% CI, 1.47-10.55] or three or more affected members (OR(wood), 4.41; 95% CI, 1.58-12.30; OR(fish), 4.27; 95% CI, 1.10-16.47). In contrast, a tendency for elevated risk was noted for betel nut use in late age-onset families (OR, 2.44; 95% CI, 1.16-5.13) and the CYP2E1 c2 allele in families with less than three affected members (OR, 2.06; 95% CI, 1.04-3.35). Risk estimates associated with these exposures were similar when the analyses were restricted to EBV-seropositive subjects. To better adjust for degree of relationship among family members and residual genetic correlations, we also calculated ORs using a variance components model. The results from the two methods were similar indicating that the risk estimates from conditional logistic regression were unbiased.