The aim of the present investigation was to determine the hydraulic properties of the Tertiary T2 aquifer and the leakage properties of the overlying confining bed of the Port Willunga Formation. A pump test, involving four production wells and one disused well in the Kangaroo Flat area, was carried out over the period 26-28 September 2000. Analysis of the pump test data was conducted by using a combination of type-curve fitting on log-log paper, and semi-log straight-line plots. Analyses made using the Cooper-Jacob semi-log, straight-line method indicated an average transmissivity of 252 square m per day and an average storage coefficient of 0.001. Comparative analyses based on the Hantush (1964) curve-matching method yielded a transmissivity value of 192 square m per day, a storage coefficient of 0.0015, and a vertical hydraulic conductivity for the confining bed of 0.0024 m/day. Both these result sets indicate that the aquifer is semi-confined and leaky. The hydraulic resistance of the confining bed was calculated at 419 days, a figure which suggests that the confining bed is highly transmissive, so therefore the potential for downward leakage is high. Thus potential exists for poor-quality groundwater in the overlying Q4 aquifer to move down through this confining bed into the T2 aquifer during periods of intense pumping of that aquifer.