A new method for absorbed-dose assessment in radionuclide therapy is presented in this paper. The method is based on activity quantification by the conjugate-view methodology, applied to serial whole-body, anterior-posterior, scintillation-camera scans. The quantification method is an extension of previous studies, and includes separate corrections for attenuation, scatter, and overlapping organs. Further development has now been undertaken to take into account the capabilities of new dual-head camera systems with a built-in X-ray tube for anatomical imaging. Furthermore, the modeling of time-activity data is included, and dosimetric calculations based on the formalism by the Medical Internal Radiation Dose (MIRD) committee. To streamline absorbed-dose assessments for a large number of patient studies, the programs for quantification, image registration, and absorbed-dose calculations have been embedded in an envelop program termed LundADose, where calculations, to a great extent, are performed automatically. Evaluation of the whole-body activity quantification is performed for patients undergoing radioimmunotherapy by monoclonal antibodies labeled with (111)In or (90)Y.