Schlesinger transformations are discrete monodromy-preserving symmetry tran
sformations of the classical Schlesinger system. Generalizing well-known re
sults from the Riemann sphere we construct these transformations for isomon
odromic deformations on genus one Riemann surfaces. Their action on the sys
tem's tau-function is computed and we obtain an explicit expression for the
ratio of the old and the transformed tau-function. (C) 2000 American Insti
tute of Physics. [S0022-2488(00)04505-9].