An important step in Internet addiction research is to develop standardized instruments for assessing Internet addiction-related symptoms. The Compulsive Internet Use Scale (CIUS) is a promising brief questionnaire. The aim of this study was to examine the factor structure of a German version of the CIUS with confirmatory factor analysis in a general population sample. In addition, the best fitting structure was tested for factorial invariance across sex, age, education level, and weekly Internet use. We used a weighted general population sample (N=8,132) of 14-64 years olds spending at least 1 hour online for private purposes per typical working or weekend day. Findings include that a one-factor model was found to fit well. It was invariant across sex, age, education level, and weekly Internet use. The findings support the validity of the CIUS as a short screening instrument.