A method of automatically diagnosing pneumonia in a patient includes using an input/output interface device to obtain values of two or more diagnostic parameters of the patient from a caregiver for the patient. The method includes using a processor coupled to the input/output interface to apply the two or more diagnostic parameters to an electronic memory storing precompiled pneumonia diagnostic models to identify an optimal diagnostic model for making a diagnosis. The values of the two or more diagnostic signs are applied to the identified optimal diagnostic model to generate a diagnosis output. The input/output interface device is operated in accordance with the diagnosis output to indicate the presence or absence of pneumonia in the patient to the caregiver. The caregiver may use the diagnosis to provide appropriate care to the patient. The pneumonia diagnostic models are derived from investigation of a population of pneumonia positive and non-pneumonia subjects.