This paper investigates the use of the concepts of similarity and dimensional analysis to interpret results from reduced-scale models of axially loaded piles embedded in sand. These concepts are reviewed in the light of a pilesoil system and its response to static or half-sine impulsive loading. It is suggested that constitutive similarity between model and prototype responses can be fulfilled without scaling gravity, provided that a stress scaling factor equal to one is selected. The scaling factors are validated with numerical simulations via finite element analyses by comparing the results from full-scale and special reduced-scale pilesoil models. It is also shown that a frustum confining vessel has the potential to provide more realistic scaled responses than are obtained with the classical 1g devices. A series of pile test responses are simulated for different pile lengths and different coefficients of lateral earth pressure. A set of scaling factors is presented and a particular set of dimensionally homogeneous π groups is proposed to characterize the behaviour of the pilesoil system. Simulated responses are interpreted using the proposed π groups to obtain functional relations relevant to the pilesoil problem.Key words: reduced-scale modelling, dimensional analysis, similarity, model piles, sands.