An analytical anion-exchange procedure has been developed for the rapid separation of acid-soluble nucleotides (the so-called "free" or tissue nucleotides). It permits assay at low pressures (275-415 kPa; 40-60 psi) in less than 1 h on 10-cm columns of Aminex resins (conventional styrene-type anion exchangers) with alkaline citrate solutions as the eluent. Separation variables have been investigated, to determine optimum conditions for the routine analysis of samples containing tissue nucleotides. Also described here is a simple solvent-extraction procedure for removing HCIO4 or CCI3CO2H quantitatively from cell extracts that contain acid-soluble nucleotides: they are removed from aqueous acid solutions with a water-insoluble amine dissolved in a water-immiscible solvent.