The burgeoning area of estimating functions is reviewed with emphasis on developments in the past two decades or so. The emphasis is on semiparametric methods. Connections with empirical likelihood (
see
Empirical Likelihood
) and the bootstrap (
see
Bootstrap: Theory
) are noted, as well as extensions of the theory to stochastic processes. There are numerous application areas where estimating functions have become very influential relatively recently. Econometrics and finance, in particular, have, especially in the past decade or so, discovered the advantages of the estimating function approach. In the statistics arena, applications in biostatistics are particularly important, while survey sampling (
see
Survey Sampling
) continues to be a source of methodological problems, which can be tackled via estimating functions.