The Internet-based Cholesterol Assessment Trial (I-CAT) is a masked, randomised, controlled trial that will include at least 3,700 consumers followed for between 8 and 16 weeks. All consumers that participate in the study will ultimately be offered the I-CAT service, which provides individually tailored information about the management of cholesterol-related risk via an interactive website. However, by offering the service immediately to one group (intervention) and delaying it by 8 weeks in the other group (control) it will be possible to precisely and reliably determine the effects of the I-CAT service on consumers and their use of cholesterol lowering interventions.