Described is the modulation of the neovascularization and/or growth of collateral arteries and/or other arteries from preexisting arteriolar connections. Methods are provided for enhancing neovascularization and/or the growth of collateral arteries and/or other arteries from preexisting arteriolar connections comprising contacting organs, tissue or cells with a colony stimulating factor (CSF) or a nucleic acid molecule encoding a CSF. Furthermore, the use of a CSF or a nucleic acid molecule encoding a CSF for the preparation of pharmaceutical compositions for enhancing neovascularization and/or collateral growth of collateral arteries and/or other arteries from preexisting arteriolar connections is described. Also provided are methods for the treatment of tumors comprising contacting an organ, tissue or cells with an agent which suppresses neovascularization and/or the growth of collateral arteries and/or other arteries from preexisting arteriolar connections through the inhibition of the biological activity of CSFs. Described is further the use of an agent which suppresses neovascularization and/or the growth of collateral arteries and/or other arteries from preexisting arteriolar connections through inhibition of the biological activity of CSFs for the preparation of pharmaceutical compositions for the treatment of tumors.