Static relative permittivities epsilon(r) of water + butane-1,2-diol, water + butane-1,3-diol, and water + butane-1,4-diol in the liquid phase were determined from capacitance measurements over the entire composition range under pressures up to 300 MPa at 298.15 K. The Tait-type equation is applied to represent the pressure dependence of epsilon(r) for each solution. The Tait-type parameters, A and B, are determined from the nonweighted least-squares method. The composition dependence of epsilon(r)(0.1), (partial derivative ln epsilon(r)/partial derivative P)(T), and epsilon(r)-(2)((partial derivative epsilon)(r)/partial derivative P)(T) values at 0.1 MPa for the three binary aqueous butanediol mixtures are compared.