This article lays the empirical and methodological basis for the development of a lexical database that analyses the derivative morphology of Old English. After revising the state of the art; the working hypotheses are established and the descriptive principles for the analysis of tranparent as well as opaque derivation are established. Finally; a step is taken in the explanatory direction by defining the parameters of the analysis of the bases and adjunts of derivation that are relevant for explanation.