Sexually transmitted infections (STIs) are major public health problems in Ethiopia. Because ofrnthe clinical problems and complications that STIs cause in individual patients, STIs requirernattention. This fact becomes even more worrying if we view STIs as a proxy indicator ofrnbehaviours placing our people at higher risk of acquiring and transmitting HIV infection.rnCurrently there are no sophisticated laboratories for examining STI infections in Ethiopia. Thernpatients are diagnosed based on proper analysis of patients back ground (history taking) andrnphysical examinations with or without laboratory support. Due to the shortage of laboratories andrnhealth service providers the patients could not receive efficient and effective treatment with lowrncost in a short period of time.rnIn this work, we have proposed a Mobile Health Advisor system (MoHA system) for STI.rnMoHA system for STI provides mobile and personal computer based advice on STI. MoHA isrnsimple to use, reachable, fast and confidential system. It incurs no extra cost for mobile users andrnPC users who have Internet access. The system allows the users to select the symptoms they arernexperiencing from a list of symptoms and send the symptoms to the server to get an advice onrnthe particular health problem identified by the system. The symptoms are sent from mobile to thernserver through the GPRS mobile network and from PC through Internet connections. The serverrnside web application provides advice to the users based on the knowledge stored in Ontologyrnthrough reasoning process.rnKeywords: MoHA system, STI, STI Ontoogy, Mobile Health