The Internet and its potential effects on society receive much attention in public discussions. Many discussants expect that the World Wide Web will enhance global trade of products and services and thus will increase economic wealth. However, social scientists are concerned with possible social side-effects of the Internet. Specifically, a recent experimental study by Robert Kraut et al. (1998) found that greater use of the Internet decreases communication within the family, diminishes the size of the subjects' local social networks, and increases feelings of loneliness and depression. This study sheds doubt on the generality of these findings. Results from a survey of 15 842 Internet users and a control group of 1196 non-users conducted in Switzerland suggest that Internet use neither decreases respondents' network size nor the time spent with friends. The study also shows that electronic mail is widely used and has positive effects on people's social networks. The study uses many socio-demographic control variables and statistical methods to control for simultaneity.