Poliovirus type 1 (Mahoney strain) has been purified by retention on a Sepharose 4B-antibody column and elution with 3M K thiocyanate. The virus was recovered in excellent yield and its purity was as high as that achieved by detergent treatment followed by sucrose gradient centrifugation. The column could be re-used and its capacity was sufficiently high to make it a useful method for the purification of milligram quantities of the virus.