- In this paper we discuss the relationship between prospective and retrospective sampling problems. Estimates of the parameter of interest may be obtained by solving suitable estimating equations under both sampling schemes. Most common examples of such estimates include the maximum likelihood estimates. Some classical results and more recent development of the first-order asymptotic relationship between the estimators are reviewed. High-order expansions are given for the distributions of the retrospective estimators. Expansions for the marginal distributions of interest are obtained for both prospective and retrospective data. Furthermore, it is shown that the two expansions are asymptotically equal, at least up to order O(n-1). This implies that readily available prospective saddlepoint methods may be applied to the analysis of retrospective data without loss of high-order accuracy. The results are also briefly illustrated numerically. 1999 Biometrika Trust.