Small mammal veterinarians in clinical practice, by nature of their specialty, often have to select diagnostic procedures that will provide the best and least expensive treatment options. A familiar course is establishing a viable list of differential diagnoses during clinical exam or necropsy based on the gross appearance of the lesions. Gross lesion recognition (and photography), like other imaging modalities, is a bit of an art form. Vast zones of grey may confront the investigator when considering what the lesion is, what it could be, and what to do with it. And nobody is good at all of it. Historically, our attempts at accurately diagnosing disease by gross lesion recognition have been a humbling experience, and that has been the impetus for all further diagnostic specialties. Gross lesions, or lack thereof, are the first visual indication of what may be wrong with the patient (or cadaver, as the case may be). These are the lumps, the effusions, the asymmetrical oddities, the discolorations, the odors of disease that (hopefully) stimulate a “scientific” thought process culminating in a list of differential diagnoses. The purpose of this 2 hour interactive workshop is to present clear and not so clear images of common and not so common gross lesions in live and necropsy specimens, and in a participatory manner, establish a differential diagnosis and means for establishing a definitive diagnosis.