A global Rayleigh-type H218O circulation model was forced by two reanalysis products, the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis and the European Centre for Medium-Range Weather Forecasts (ECMWF) 15-year reanalysis (ERA15) data sets, and the Global Network of Isotopes in Precipitation database was used to validate for 1979--1993 on monthly to interannual scales. Over Europe, ERA15 better matched observations at both timescales, owing mainly to better precipitation fields in ERA15, while in the tropics both produced similarly accurate isotopic fields. The isotope analyses diagnose accuracy of two-dimensional water circulation fields in data sets with a particular focus on precipitation processes but in a slightly different manner over middle and high latitudes than over low latitudes: Analyses were more severe over the former regions.