Prepn. of the title compds., useful for the remission of pain, bleeding tendency, and fever, is described. Orthophosphoric acid (85%) is dehydrated; MeCN and Et3N added and the mixt. cooled to -20.degree. and ClCO2Et in MeCN added. The mixt. is stirred 0.5 hr followed by the addn. of prednisolone in MeCN and Et3N. The mixt. is refluxed 1 hr, and 2N NaOMe in MeOH added to yield Na salt of prednisolone 21-phosphate, m. 200.degree.. Similarly are prepd. 6 addnl. analogs.