We show that there exists a finite set S of finite posets such that the following holds. Whenever, ( Y,⩽) is not isomorphic to a member of S and it is not trivially ordered then for every finite group G there exists a finite poset ( X,⩽) which has no induced subposet isomorphic to ( Y,⩽) such that G is isomorphic to the automorphism group of ( X,⩽). For some members ( Y,⩽) of S we give necessary and sufficient conditions for a group G to be isomorphic to the automorphism group of a finite poset ( X,⩽) which has no induced subposet ( Y,⩽). This includes the classification of the automorphism groups of finite interval orders and series- parallel posets.