The control of the microstructure of BaTiO3 films grown on titanium by the hydrothermal-electrochemical method was investigated. Experiments were conducted in a three-electrode high-pressure electrochemical cell in a 0.1M Ba(OH)(2) electrolyte at 150 degreesC. Results showed that the spontaneous initial nucleation linked to pure hydrothermal BaTiO3 formation can be inhibited by cathodically protecting the titanium electrode from the moment it is immersed in the electrolyte. The application of initial nucleation pulses of varying cathodic potentials affected the grain size of the deposit. It is suggested that the formation of a titanium oxide layer is a necessary step previous to the nucleation of BaTiO3.