Petrography and strontium content of 62 samples of oolitic limestone from many parts of the world were studied systematically. Strontium content of carbonates decreases with age. Apparently strontium is lost during diagenesis and this loss may be related to conversion of aragonite to calcite. Maximum loss of strontium occurs before any major episode of cementation. The percentage of strontium in ancient oolites may not be related to recrystallization but strontium is about twice as abundant in cement as in allochems in ancient sediments.