Vertical bipolar junction structures, methods of manufacture and design structures. The method includes forming one or more sacrificial structures for a bipolar junction transistor (BJT) in a first region of a chip. The method includes forming a mask over the one or more sacrificial structures. The method further includes etching an opening in the mask, aligned with the one or more sacrificial structures. The method includes forming a trench through the opening and extending into diffusion regions below the one or more sacrificial structures. The method includes forming a base region of the BJT by depositing an epitaxial material in the trench, in contact with the diffusion regions. The method includes forming an emitter contact by depositing a second epitaxial material on the base region within the trench. The epitaxial material for the emitter region is of an opposite dopant type than the epitaxial material of the base region.