This study proposes a stochastic mixed-integer linear programming approach to maximise the total expected profit of a price-maker Hydro Generating Company. Start-up and shutdown procedures, discrete hydro unit-commitment constraints, ramp rates, minimum and maximum power output constraints, and head effects, are all taken into account in an efficacious way. Uncertainties are modelled considering sets of scenarios to describe the residual demand curves. The proposed approach is successfully applied to a Portuguese hydro system in cascaded configuration. Conclusions are duly drawn.