Background Internet addiction is a serious and growing problem. There is an emerging public health concern over the increase in Internet usage, particularly among adolescents. Aim The purpose of this study was to assess the pattern of Internet use among university students and to evaluate the personality and the associated psychiatric disorders with students of Internet addiction. Participants and methods A total of 300 medical students were subjected to the Internet Addiction Test (IAT) developed by Young in 1998. Personality evaluation by Eysenck Personality Questionnaire and psychiatric interview by Arabic version of Mini-International Neuropsychiatric Interview were done for Internet addicts to assess any associated personality or psychiatric disorders. Results Students were divided into four Internet user groups according to their IAT total scores: normal Internet users (n=117, 39.0%), mild Internet addicts (n=116, 38.7%), moderate Internet addicts (n=64, 21.3%), and severe Internet addicts (n=3, 1.0%). Males were more prone than females to develop severe forms of Internet addiction. Family environment had a major effect on developing Internet addiction. Neurotics and introverts were more susceptible to develop Internet addiction than others. Depression and anxiety were significantly associated with Internet addiction. Conclusions This study suggests that students who use the Internet excessively exhibit significantly more psychiatric symptoms than students who use the Internet less frequently. In addition, pathological Internet addicts appear to have a distinctive personality and social profile when compared with nonpathological users.