Although the Internet has become a forum for making sexual contacts, and has been associated with increased sexually transmitted infection (STI) transmission, we have little information of history of STIs in Internet-based samples. The Internet behaviours that are associated with STI acquisition are poorly understood. We analysed STI histories reported by 904 Swedish men and 931 Swedish women who responded to an Internet-based survey on sexual behaviour in 2002: 16.6% of men and 22.5% of women reported a lifetime history of STIs, with Chlamydia being the most common for both genders. 3% of men and 5% of women who reported an STI, indicated that they had had more than one. Sources of the STI, where known, were Internet-acquired partners in only 3% of cases. There were no differences between men and women with or without an STI history regarding the kind of online sexual activities they engaged in, how they found sexual material online, and the reasons they engage in sexual activities. These rates are similar to those reported in a national random study of sexuality in Sweden. Contrary to prior research, these results suggest no relationship between STI and specific Internet characteristics usage patterns. These data suggest that the Internet is not yet a major source of STIs in Swedish men and women. Given these STI histories, the Internet may be a useful medium to include in STI prevention efforts.