The present invention relates to the use of Rspondins, particularly Rspondin2 (Rspo2) or Rspondin3 (Rspo3) or Rspondin nucleic acids, or regulators or effectors or modulators of Rspondin, e.g. Rspo2 and/or Rspo3 to promote or inhibit angiogenesis and/or vasculogenesis, respectively. The invention is based on the demonstration that Rspo3 and Rspo2 are angiogenesis promoters, and the identification of Rspo2 and 3 as positive regulators of vascular endothelial growth factor (VEGF). These results indicate a major role for Rspondins, particularly Rspo3 and/or Rspo2 in the signaling system during angiogenesis. The invention also relates to the use of regulators or effectors or modulators of Rspondin3, including agonists and antagonists, in the treatment of conditions where treatment involves inhibiting or promoting angiogenesis and/or vasculogenesis.