The chapter discusses the analysis of sexual contact networks, which are characterized by a scale-free distribution of the number of sexual partners. Using data from a 1996 Swedish survey of 4781 individuals, the authors find that both females and males exhibit a power-law distribution with similar exponents ($\alpha \approx 2.4$) for the number of partners over a twelve-month period. This scale-free nature suggests that strategic interventions, such as targeted safe-sex education campaigns, may be more effective in preventing the spread of sexually transmitted diseases. The study also highlights the small-world phenomenon, where networks have short average path lengths but high clustering, and the implications for disease propagation and control in scale-free networks. The findings challenge the traditional concept of a "core group" in epidemiological studies and emphasize the need for tailored strategies to manage the dynamics of sexual contact networks.The chapter discusses the analysis of sexual contact networks, which are characterized by a scale-free distribution of the number of sexual partners. Using data from a 1996 Swedish survey of 4781 individuals, the authors find that both females and males exhibit a power-law distribution with similar exponents ($\alpha \approx 2.4$) for the number of partners over a twelve-month period. This scale-free nature suggests that strategic interventions, such as targeted safe-sex education campaigns, may be more effective in preventing the spread of sexually transmitted diseases. The study also highlights the small-world phenomenon, where networks have short average path lengths but high clustering, and the implications for disease propagation and control in scale-free networks. The findings challenge the traditional concept of a "core group" in epidemiological studies and emphasize the need for tailored strategies to manage the dynamics of sexual contact networks.