A new killed, purified, poliomyelitis virus vaccine is described. The viral antigens are essentially pure and are precisely measured to provide vaccine of uniformly high potency. The vaccine is free from detectable monkey-kidney antigen, so that the theoretical problem of renal autoimmunization is obviated. Two 0.5ml. doses of vaccine given 1 month apart elicited significant neutralizing antibody responses to the Parker Type-I poliovirus in 98% (52 out of 53) of initially sero-negative children. Comparable responses were found with respect to the Type-II MEF-1 and Type-III Saukett types. The authors believe that this purified vaccine answers the urgent need for a poliomyelitis vaccine that will consistently, rapidly, and safely immunize essentially all recipients against all 3 poliovirus types.