The National Cholesterol Education Program (NCEP) emphasizes regular physical activity to reduce coronary heart disease (CHD) risk associated with the metabolic syndrome. Despite the clear health benefits, most adults do not engage in physical activity (PA) at the recommended level. The purpose of this pilot study was to evaluate the effects of a physical activity Internet intervention on: (1) PA minutes per week, and kilocalories expended per week, (2) lipid, and hsCRP biomarkers, and (3) self-efficacy to engage in PA, and self-efficacy to overcome barriers to PA participation in the metabolic syndrome population. A secondary purpose was to evaluate participants' acceptance and perceptions of the Internet intervention for a larger study. The theoretical framework of the intervention was Bandura's Social Cognitive Theory. An experimental repeated measures design was used to examine outcomes pre and post intervention (6 week duration). Participants were randomly assigned to the usual care group (n=10) or the Internet intervention group (n=12). Participants were 16 males and 6 females recruited from a cardiology clinic, ranging in age from 32-66 years. PA minutes per week and kilocalories expended per week in moderate or greater intensity PA were measured by the 7-Day Physical Activity Recall. Total kilocalories expended per week at all intensity levels were measured by the RT3 Accelerometer. Analyses involved calculating change scores (post minus pre intervention scores) and using non-parametric statistics to compare group differences. Although no significant differences were found in the intent-to-treat analysis due to the small sample size, trends favoring the intervention group were found in adherence with PA minutes per week, kilocalories expended per week, card iorespiratory fitness, HDL cholesterol, and self-efficacy for PA. Significant improvements were found in the per-protocol analysis in the intervention group in HDL cholesterol (z=-2.024; p=.04), and self-efficacy for PA (-1.970; p=.04). Participants reported overall positive perceptions of the intervention. Further development and testing of this evidence-based Internet intervention in a larger study is needed to fully investigate the effect on PA outcomes, and thus reduce CHID risk in the metabolic syndrome population.