Motivated by a design for discovering associations between inherited childh
ood risk factors and adult-onset disease, the problem of estimating the dis
tribution of age at onset of the disease from a case-control sample of subj
ects who have and have not yet experienced onset is examined. An embedding
of the distribution function of age at onset in a multiplicative intercept
model simplifies estimation by allowing the distribution function of age at
enrollment to be conditioned out of the likelihood. A class of estimators
of the distribution function of age at onset is developed and it is argued
that a member of the class is efficient. Standard error calculations and an
approach to approximating the efficient member of the class are described.