The human vomeronasal duct (VND) is described as a tubular or pouch-like mucosal invagination of the anterior nasal septum. This study investigated shape, size and orientation of the VND using magnetic resonance imaging (MRI). Fifteen subjects participated (eight women, seven men; mean age 39 years, age range 18-66 years); they had been pre-selected with regard to the presence of a VND opening of 1 mm. MRI was performed before and after application of diluted gadolinium-diethylene-triamino-penta-acetic actetate (Gd-DTPA) into the left or right VND. A tubular structure was found in 12 subjects with a median length of 7 mm (range 3-22 mm; one VND with a length 47 mm). In three subjects a nearly circular, pouch-like structure was observed. Seven of the tubular VNDs were slightly bent upwards, the other five VNDs ran parallel to the floor of the nasal cavity. There was no significant gender-related difference in the length of VNDs. These data indicate considerable variability of shape, size and orientation of the human VND.