The MIPs modelling methodology is the most innovative and comprehensive approach to hillslope and catchment modelling to be developed in the last decade. It has produced good results for early plot and catchment applications at the small Gårdsjön site in Sweden but needs further testing against well-controlled data on the dynamic responses of both flow and transport. This is, of course, difficult in the field where the boundary conditions at profile, plot, hillslope and catchment scales can be poorly defined. The approach allows different model hypotheses will be tested, within a framework to take proper account of the uncertainties in the observational data. The MIPs modelling methodology provides an important opportunity for modellers and field researchers to collaborate, something that has been suggested as lacking in hydrological science in the past