CONTEXT: Low adiponectin levels predict type 2 diabetes, and one prospective study in men reported its independent prediction of vascular events. Many observers thus already consider adiponectin to be a major part of the "common soil" underpinning diabetes and vascular disease. OBJECTIVE: The objective of this study was to assess the association between adiponectin and incident coronary heart disease (CHD) risk in the British Women's Heart and Health Study. DESIGN: This was a prospective (4 yr) case (n = 167) control (n = 334) study nested within the 4286 women in British Women's Heart and Health Study. SETTING: The study was performed in a primary care setting. PARTICIPANTS: The study consisted of women (n = 4286) randomly selected from 23 British towns between 1999 and 2001, who were 60-79 yr of age at baseline. MAIN OUTCOME MEASURES: Association of adiponectin with CHD risk factors and incident CHD events were the main outcome measures. RESULTS: Among both cases and controls, adiponectin positively correlated with age and high-density lipoprotein cholesterol and inversely correlated with waist to hip ratio, fasting insulin, fasting glucose, homeostasis model assessment of insulin resistance scores, C-reactive protein, and triglycerides. However, despite adequate power and these associations with CHD risk factors, adiponectin did not predict CHD events in unadjusted or adjusted analyses. The relative risk ratio for a doubling of adiponectin was 0.93 (95% confidence interval, 0.78, 1.11). CONCLUSIONS: It is premature to consider adiponectin as a root for vascular disease in women despite its association with insulin resistance and diabetes. Additional prospective studies are required to determine whether there is a true sex difference in the effect of adiponectin on CHD.