Cardiovascular diseases are still the most common cause of death in developed countries. During the development of heart failure, hypertension, as well as other diseases associated with endothelial dysfunction, e. g. diabetes mellitus, miscommunications between the different cardiovascular cell types and alterations in intracellular signal transduction cascades occur. Heterotrimeric G proteins and monomeric GTPases are pivotal mediators in such signaling cascades in all cardiovascular cell types and thus contribute to the propagation of pathological alterations. We therefore analyze such signaling pathways and their alterations, e.g. in endothelial cells, pericytes and vascular smooth muscle cells.