A Deep Learning algorithm for automatic segmentation of the prostate and its peripheral zone (PZ) is investigated across MR images from two MRI vendors. The proposed architecture is a 3D U-net that uses axial, coronal, and sagittal MRI series as input. When trained with Siemens MRI, the network achieves a Dice similarity coefficient (DSC) of .91 and .76 for the segmentation of the prostate and the PZ respectively. However, the network performs poorly on a GE dataset. Combining images from different MRI vendors is of paramount importance to pursue a universal algorithm for prostate and PZ segmentation.