The aim of hydrological research has always been, and should still be to improve our understanding of hydrologic processes. Catchment hydrological response has the potential to enhance understanding of these processes. Regionalisation of hydrological response is important in identifying watersheds with similar catchment hydrological response, thus making predictions in ungauged and poorly gauged basins to be possible. This study establishes the hydrological response of 122 catchments in Swaziland's trans-boundary basins on the basis of validated WR90 hydro-meteorological time series data. The flow duration indices (FDIs: Q10, Q50, Q90) were determined and standardised by the mean monthly streamflow, and the runoff ratio was calculated as a method to determine how catchments respond to precipitation inputs. The runoff ratio and FDIs were then plotted against aridity indices, and the plot shows that the runoff ratio is consistent with the aridity index, except for a few suspected anomalies emanating from values of Q50 and Q90. The findings indicate that the hydrological response of the catchments is diverse and somewhat characterised by regions. The diversity and the regions are associated with climate regime and topography controls. It is anticipated that the potential of using hydrological response to gain more understanding of catchments behaviour will improve and further rigorous exploration may be required.