Morphometric data are presented on 300 solution flute sets developed at 21 sites worldwide on the three main groups of soluble rocks, namely limestone, gypsum and salt. Lithological control is shown to create significant differences in flute form between the rock groups, and also within individual rock groups and local sites. Climatic control of flute form is shown by previously published data. The means by which these controls are exerted is as yet unclear. Further research relating detailed rock properties to flute form is required in order to elucidate such controls.