Here we report an attempt to quantitate the relative contributions of the history, physical examination and investigations in making medical diagnosis. In this prospective study of 100 patients, with new or previously undiagnosed conditions, we listed their differential diagnosis with confidence score; after the history, after physical examination and after the investigations. In two patients no definite final diagnoses could be arrived even after extensive investigation--these two cases were excluded from the study. In seventy seven patients (78.58%) patients, the history led to diagnosis. The physical examination led to diagnosis in eight patients (8.17%); and investigations led to diagnosis in 13 patients (13.27%). The confidence in correct diagnosis increased from 6.36 on a scale of one to ten after the history to 7.57 after physical examination and 9.84 after investigations--implying that history, physical examination and investigation have their own limitation at each stage and an integrative approach is needed in making a medical diagnosis with more emphasis on history.