Background: IE is a disease characterized by high morbidity and mortality. Rapid diagnosis, effective treatment, and prompt recognition of complications are essential to good patient outcome. Differentiating IE from its mimics is important to avoid over or under diagnosis of IE with the consequent catastrophic implications. Aim of the study:Through analyzing the database of Kasr Al-Aini infective endocarditis project, (IEP) the main aim of this work was to Identify the spectrum of diseases that could mimic IE, Detect clinical, laboratory and echocardiographic features that may aid in differentiating infective endocarditis from other mimicking diagnoses. Also to determine the inhospital and long term outcome of endocarditis-like diseases.Methods:The data of 197 patients referred to Kasr Al-Aini IEP between February 2005 till December 2008 with a suspicion or diagnosis of IE was analyzed. Patients were divided according to modified Duke criteria into definite endocarditis (IE group; n = 160) and rejected endocarditis (non-IE group; n = 31). Case report forms were analyzed to collect various clinical, laboratory, microbiologic and echocardiographic features. Inhospital course was recorded. Long term Follow up was conducted to identify the clinical outcome of both groups and to ascertain the original rejection of IE in the non-IE group.Results and conclusion:Among patients referred to Kasr Al-Aini IEP, patients with endocarditis-like diseases represented one sixth of all enrolled patients, Chest infection, acute rheumatic activity, genitourinary tract infection and autoimmune diseases represent the commonest endocarditis mimics. Almost half of patients presented with major complications and one sixth developed new major complications during hospitalization, patients with endocarditis-like diseases had better response to medical therapy, less need to early cardiac surgery during hospitalization and a trend towards higher need for late cardiac surgery.. Patients with and without endocarditis had similar long term composite outcome in term of hospitalization, cardiac surgery and total mortality.