The hydrodynamic dispersion coefficients in groundwater aquifers can be determined from observed values of solute concentrations. For a two-dimensional aquifer in which the concentrations of a solute are known an algorithm is developed to determine the values of longitudinal (∈L) and transverse (∈T) dispersivities. Concentration polynomials are developed by using double interpolation for a set of selected values of longitudinal and transverse dispersivities. With two of the polynomials, Newton's method is used to find the roots which are the values of the longitudinal dispersivity and the ratio of ∈L to ∈T. With more than two polynomials an optimization approach is used in arriving at the values of ∈L and ∈L/∈T. The methods converge to the true values for a good initial estimate of the values.