On symplectic transformations

This is an English translation, prepared by Wilberd van der Kallen, of the 1951 thesis by T.A. Springer. In this thesis Springer studied the classification of conjugacy classes in the symplectic group $Sp_n(K)$, where the commutative field $K$ is of characteristic different from 2. He finds that each conjugacy class is characterized by a system of invariants. These invariants are first of all -- as in the case of the general linear group -- irreducible polynomials and systems of non-negative integers, but secondly also equivalence classes of certain Hermitian forms and of certain quadratic forms. Original Dutch title: Over symplectische transformaties.