Disease incidence (new cases of disease per person per year) is usually mea
sured by using longitudinal data. However, several recent proposals for mea
suring the incidence of human immunodeficiency virus (HIV) rely on cross-se
ctional data only. These methods assume each person is only sampled once; h
owever, in some instances, it is necessary to consider these cross-sectiona
l methods when individuals are represented more than once in the survey sam
ple. We derive an extension of the cross-sectional incidence estimator that
is valid for data from repeatedly screened populations and show under what
conditions our new estimator reduces to the old estimator. An example invo
lving estimation of HIV incidence among repeat blood donors is presented.