Seco-baccatin III derivatives of formula: ##STR00001## wherein R, R.sub.1-R.sub.4, .[.R.sup.1.]. .Iadd.R'.Iaddend., .[.R.sup.11.]. .Iadd.R''.Iaddend., and .[.R.sup.111.]. .Iadd.R'''.Iaddend. are disclosed herein; pharmaceutical compositions comprising seco-baccatin III derivative; and methods for treating cancer, arthritis, and inhibiting angiogenesis in an animal comprising administrating to a patient in need thereof a therapeutically effective amount of a seco-baccatin III derivative are disclosed.