The paper examines a framework of approach within which landsurface analysis may be undertaken in the humid-temperate northern half of the North Island, New Zealand; an area exhibiting a wide range of lithologies and surface cover, with evidence of recent and current tectonic and volcanic activity, and undergoing active geomorphic processes'. The largely theoretical formulations of W. M. Davis, W. Penck and L. C. King are considered briefly and are rejected on both theoretical and practical grounds. General systems theory encompasses certain concepts and systems properties which have been applied by a number of geomorphologists. The open system property of dynamic equilibrium is examined, and is found to be inapplicable to the total landsurface of this region. The concepts of environment and sub-system are introduced and their relevance to the region illustrated by a physical hillslope model. Dynamic equilibrium is considered to be a possible state of certain hillslope sub-systems. Construction of a mathematical model to describe the total landsurface or the entire hillslope system is not feasible until hillslope sub-systems have been analysed. The form of a linear regression model applicable to hillslope sub-systems is introduced, and it is suggested that the pattern of the residuals from regression may be used as a statistical technique to assist in identifying .significant system boundary conditions, and to provide a quantitative indication of the influence of historical factors.