New diagnostic techniques, Computerized Axial Tomography (CAT), Nuclear Magnetic Resonance (NMR) and their potential application to marine mammals are discussed with emphasis placed on limitations of each technique. Their clinical need is then compared with other techniques such as endoscopy, ultrasound and radiography. Animal limitations concerning the latter techniques are discussed with case reports. It is seen that each visualization technique has limitations that the clinician must recognize to make the best use of each diagnostic method.