Abstract: A method of preparing a formaldehyde substituted hydantoin in the form of a liquid antimicrobial preservative solution is disclosed. The inventive solution prepared by the disclosed method comprises a condensation product of a 5,5-disubstituted hydantoin and formaldehyde prepared in the presence of an antimicrobial liquid phenylic or benzylic alcohol. The inventive solution inhibits or retards microbial growth when an effective microbial inhibiting amount is subsequently added to a medium capable of supporting undesirable microbial growth. Preferably the inventive solution contains 1,3-dimethylol-5,5-dimethyl hydantoin prepared in the presence of phenoxyethanol and including an effective antimicrobial amount of at least one paraben preservative prepared by an embodiment of the disclosed method.