SummaryUniformly labeled (U) 14C nicotinamide adenine dinucleotidc phosphate (NADPt) was synthesized by phosphorylating [U-'4C]nicohnarnide adenine dinucleotide (NAD+) in the presence of immobilized NAD+ kinase. The 15 pCi (600 pL) synthesis consistently achieved yields between 808 and 85% and radiochemical purities greater than 95%. The IU-14ClNADP+ was purified by high performance anion-exchange chromatography using a gradient elution of ammonium bicarbonate. This procedure may be applicable to the synthesis of other charged, W-absorbing products of enzymecatalyzed reactions.