Beitr\"age zur Algebra und Geometrie Contributions to Algebra and Geometry Volume 35 (1994), No. 2, 315-331. On Conformally Flat Hypersurfaces and Guichard's Nets U. Hertrich-Jeromin Abstract A local classification result for conformally flat hypersurfaces in a four dimensional space form is obtained: they are characterized by the existence of special principal curvature coordinates. By means of conformal coordinate charts these coordinates are related to (conformal classes of) Guichard nets in Euclidean three space which reflect some geometric properties of the conformally flat hypersurface.