This article reviews the authors' experiments on calcium oxalate growth at lipid monolayers. Calcium oxalate is the principal mineral component of most urinary Stones. Membrane constituents associate either actively or passively with calcitic minerals during stone formation, and it has been proposed that lipid assemblies play a significant role, possibly providing sites for the initial nucleation event. Langmuir monolayers allow systematic studies of the heterogeneous precipitation of calcium oxalate at lipid assemblies. The influences of the chemical identity of the lipid headgroup, the organization of the monolayer, and the presence of heterogeneities and phase boundaries within the monolayer have been explored.