A double-disk tension infiltrometer is developed to measure simultaneously one-dimensional (1-D) and three-dimensional (3-D) infiltration subject to identical initial and boundary conditions. The hypothesis that cumulative three-dimensional infiltration is proportional to the square root of time is incorrect after a few seconds, and in consequence, estimates of sorptivity based on this hypothesis are in error. In contrast, sorptivity calculations using a recently developed 3-D infiltration equation that includes the edge effects of the disk give accurate estimates of sorptivity. The difference between 3-D and 1-D cumulative infiltration is used to calculate the value of an additional infiltration parameter from the double-disk experiment. This parameter, together with the sorptivity, provides the information required to calculate the contribution of gravitational flow during three-dimensional infiltration. It is shown that estimation of hydraulic conductivity using a quasi-steady-state solution may not be justified when 3-D infiltration is dominated by capillary flow effects. Finally, an analysis of the different timescales governing disk infiltrometer experiments under most practical circumstances is provided. A simple expression is given for the time at which the infiltration rate is within a specified amount of the final steady rate. ¿ American Geophysical Union 1995.