Conditions for the synthesis and purification of monoiodocarnosine (MIC) were examined by high performance liquid chromatography (HPLC). When carnosine (β-alanyl-L-histidine) was iodinated to obtain MIC, the maximum yield was attained by the equimolar reaction of carnosine with I₂ in 0.5 N NaOH solution. The synthesized MIC was separated by preparative reversedphase HPLC with H₂O-MeOH (90 : 10) as the eluent and then purified by recrystallization. Chemically pure MIC was obtained in 72% yield in a short time.