The extent to which commodity supplies and input demands are interrelated in Sri Lankan peasant agriculture is explored in this paper. Using a miltiproduct dual model, a seemingly unrelated system of product supply and input demand equations is estimated for four crops and five variable inputs. Restrictions based on competitive behaviour and a twice-continously-differentiable productions function are maintained in the estimation. A large number of important interrelationships in individual product supples and unput demands are identified, further documenting the need to account for intercommodity production relationships in econometric and simulation studies and in policy formulation.