Camera calibration is a fundamental task in photogrammetry and computer vision. This paper presents an approach for the automatic estimation of interior orientation from images with three vanishing points of orthogonal directions. Extraction of image line segments and their clustering into groups corresponding to three dominant vanishing points are performed without any human interaction. Camera parameters (camera constant, location of principal point, two coefficients of radial lens distortion) and the vanishing points are estimated in a one-step adjustment of all participating image points. The approach may function in a single-image mode, but is also capable of handling input from independent images (i.e. images not necessarily of the same object) with three and/or two vanishing points in a common solution. The reported experimental tests indicate that, within certain limits, results from single images compare satisfactorily with those from multi-image bundle adjustment.