This paper presents a new and simple moment method for analyzing breakthrough curves for step inputs. An advantage of moment analyses, in general, is that the underlying physical model is not needed, unlike other techniques such as fitting convective (or advective) dispersion equations. Therefore moment calculations allow multispecies (such as partitioning tracers) to be considered in one, two, or three dimensions. Previous analyses using moments have emphasized the response for a pulse input. Generally, the travel (residence) time is of importance, and previous solution techniques do not perform well for long pulse or step inputs. In this paper the presented method is used to analyze breakthrough curves for step inputs, and the results are compared to fitted analytical solutions for the one-dimensional convection dispersion equation. Only negligible differences between the new moment method and the fitted analytical solutions are found for both simulated and experimental data. Superior performance over previous methods used for evaluating moments for step inputs is demonstrated. ¿ 1999 American Geophysical Union