The ash from municipal sewage sludge incineration was calcined 3 hrs. with CaO added in amts. making PO43-/Ca2+ = 2:1 by wt., at 600, 700, 800, 900, or 950 degrees C, to yield calcinates contg PO43- 30.3-31.6, Fe 2.9-5.6. and Ca(2+)14-16.2116. These leached 4 hrs. with aq. 15% HNO3 (ash/acid = 0.3 by wt.) and centrifuged, gave solids contg. PO4 (3-) 8.1-15.7, Fe 2.6-7. and Ca2+ 6.1-7.8%. The leaching effect was not related to calcination temp. The HNO3 extn. efficiency exceeded 80%. With the 2:1 CaO in the incinerate calcined at 950 degrees C, the selectivity of extn of P with respect to Fe rose by a factor of 10, as compared with the no-CaO case.