Abstract: An allylbiguanide polymer having the following formula: ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 stand, independently of each other, for a hydrogen atom, a substituted or non-substituted aliphatic hydrocarbon group, a substituted or non-substituted alicyclic hydrocarbon group or a substituted or non-substituted aromatic group and n represents an average degree of polymerization of at least 2, or an acid addition salt thereof. The polymer may be obtained by polymerizing an allylbiguanide compound of the formula shown below or an acid addition salt thereof at a pH of 5 or less, ##STR2## wherein R.sup.1, R.sup.2 and R.sup.3 have the same meaning as above.

Abstract: A biguanide group-containing polymer having repeat units of the following general formula (I): ##STR1## wherein A represents a radical selected from the group consisting of ##STR2## where R.sup.1, R.sup.2 and R.sup.3 independently from each other represent a hydrogen atom, an alkyl group having 1-18 carbon atoms, an alkoxycarbonylalkylene group having 3-18 carbon atoms, an alkylenecarboxylic acid group having 2-18 carbon atoms or an aryl group having 6-8 carbon atoms, and ##STR3## where R.sup.1, R.sup.2 and R.sup.3 have the same meaning as above and X represents an acid,B represents a radical selected from the group consisting of --NH.sub.2 and --NH.sub.2 Y where Y represents an acid, and m and n independently from each other are integers of 1 or more with the proviso that (m+n) is 10 or more.The polymer may be prepared by reacting polyallylamine with a guanyl-O-alkylisourea compound to convert a portion of the amino groups of the polyallylamine to biguanido groups.