Background - Warfarin therapy requires frequent monitoring and dose adjustment. Elderly patients with atrial fibrillation, prior stroke, and lower literacy skills may have difficulty reading brochures that explain dosing instructions, procedures to follow, and the risks and benefits of anticoagulants. In general, it is recommended that brochures be written at or below the 6th-grade level. We determined the readability of patient information material being offered to patients receiving anticoagulants. Methods and Results - We used the SMOG grade formula to measure readability of written patient materials. We obtained 50 brochures commonly used in anticoagulation management units from industry and health advocacy groups. Patient information was related to atrial fibrillation (16%, n=8), warfarin (44%, n=22), low-molecular-weight heparins (12%, n=6), or other related topics (28%, n=14). The mean readability was found to be grade 10.7 (95% CI 10.1 to 11.2); none had a readability score at the 6th-grade level or below, 12% of the brochures had readability scores at the 7th- to 8th-grade levels (n=6), 74% at the 9th- to 12th-grade levels (n=37), and 14% at higher than 12th-grade level (n=7). The readability grade level was similar for brochures produced by industry or health advocacy groups (P=0.9) but higher for information obtained from the Internet (12.2 ± 1.3 grades) compared with other sources (10.3 ± 2.1 grades; P=0.01). Conclusions - Patient education materials related to the use of anticoagulants are written at grade levels beyond the comprehension of most patients. Low-literacy brochures are needed for patients on anticoagulants.