OBJECTIVES: To explore barriers to multiple advance care planning (ACP) steps and identify common barrier themes that impede older adults from engaging in the process as a whole. DESIGN: Descriptive study. SETTING: General medicine clinic. San Francisco County. PARTICIPANTS: One hundred forty-three English and Spanish speakers aged 50 and older (mean 61) enrolled in an advance directive preference study. MEASUREMENT: Six months after reviewing two advance directives, self-reported ACP engagement and barriers to each ACP step were measured with open- and closed-ended questions using quantitative and qualitative (thematic content) analyses. RESULTS: Forty percent of participants did not contemplate ACP, 46% did not discuss with family or friends, 80% did not discuss with their doctor, and 90% did not document ACP wishes. Six barrier themes emerged: perceiving ACP as irrelevant (84%), personal barriers (53%), relationship concerns (46%), information needs (36%), health encounter time constraints (29%), and problems with advance directives (29%). Some barriers were endorsed at all steps (e.g., perceiving ACP as irrelevant). Others were endorsed at individual steps (e.g., relationship concerns for family or friend discussions, time constraints for doctor discussion, and problems with advance directives for documentation). DISCUSSION: Perceiving ACP to be irrelevant was the barrier theme most often endorsed at every ACP step. Other barriers were endorsed at specific steps. Understanding ACP barriers may help clinicians prioritize and address them and may also provide a framework for tailoring interventions to improve ACP engagement. © 2008, The American Geriatrics Society.