The Internet is well known as a double-edged sword. It offers great convenience and efficiency to people's life and work, but creates many problems among users. Some Internet users suffer from damage to their psychological and physical health due to Internet addiction (IA), which is metaphorically comparable with the damage caused by drug addiction, and requires professional intervention. Research indicates that the group most vulnerable to IA is the youth, including university students. This paper therefore aims to explore (i) the prevalence of IA among undergraduate students, (ii) the impacts of excessive Internet use on the students, (iii) the primary Internet activities that make students addicted to the Internet, and (iv) whether the students are aware of IA, or able to cope with discomfort caused by Internet overuse. To answer these questions, a total of 350 Chinese undergraduate students located in the city of Guangzhou were sampled and asked to fill out Young's eight-item Internet Addiction Diagnostic Questionnaire (IADQ). Three addicted Internet users in addition to three normal Internet users were chosen from the sample for a semi-structured interview. The results demonstrate that 10% of the respondents are suffering from IA, and the same percentage is at risk of becoming addicted to the Internet. Significantly, the use of social networking sites highly increases the risk for IA among university students. The findings of this study will allow students and health counsellors to recognise those who are addicted or may potentially become addicted to the Internet, and adopt timely intervention or treatment to prevent further development of IA.<p></p>