A study has been made of the effects of column loading and eluting agent on the cation-exchange separation of the alkaline earths—beryllium, magnesium, calcium, strontium, barium, and radium. The principal eluting agents tested were ammonium lactate, ammonium citrate, and hydrochloric acid. Dowex-50 resin (Ion X, 300–400 mesh) was used throughout the investigation, and the column temperature was maintained at approximately 80 °C. Under optimum conditions, involving the use of 0.25 g. of resin per milliequivalent of sample and with ammonium lactate eluant (0.55 M at pH 5 for beryllium, and 1.5 M at pH 7 for magnesium, calcium, strontium, barium, and radium), a quantitative separation of all six elements in a single sample is possible in 5 hours. This procedure has been applied to the routine analysis of Sr90 in bulk milk ash samples, containing 20 mg. of strontium carrier, with yields of 85–95%. By the same method trace amounts of strontium naturally occurring in milk have also been determined.