After reviewing the matrix, it was clear that grouping diseases based on specific history and physical findings limits the differential diagnosis. The most important factors included disease incidence, timing of onset, nodular or diffuse, pain, and overlying skin changes. With this algorithm, the differential diagnosis can be limited from 28 to 7 or fewer likely diagnoses for a given presentation. Implications for Practice Bilateral parotid disease has a wide differential diagnosis with an expanding number of available tests. An algorithm, based solely on data obtained from the history and physical examination in the first patient encounter, may reduce the differential and aid the clinician in deciding on further workup and treatment. Following the algorithm presented here should allow the clinician to arrive at a diagnosis rapidly without ordering unnecessary tests and wasting resources.