Electrolytic manganese dioxide (EMD) nucleation and growth on titanium substrates from acidic manganese sulfate solutions was studied at 65oC and 90oC at different potentials and sulfuric acid concentrations. Electrochemical experiments allied to SEM examination were performed to characterize the mechanism of nucleation and its evolution with time. The EMD powder produced after a constant charge electrolysis of 448 mA·h was analyzed by SEM, BET, DTA/TG and X-ray diffraction. Results indicated that depending on the experimental conditions nucleation can be either progressive or instantaneous and when three-dimensional nuclei were formed the manganese dioxide deposit presented a higher specific surface area. Surface areas ranging from 51.8 to 168.8 m2/g were obtained under the conditions tested.