e22550 Background: An accurate assessment of family history of cancer is essential in assigning cancer risk, and in decision making regarding the timing and method of cancer screening. However, obtaining a complete and accurate cancer-related family history, including first- and second-degree relatives, is often challenging in underserved communities. Familial dynamics such as single parent households, kinship care, and estrangement may act as barriers to an individual’s knowledge of their family health history. Presently, Electronic Medical Record systems constrain users to a binary documentation of cancer history as either ‘yes’ or ‘no’. However, patients may be unaware or uncertain of their family’s cancer history. These unknowns are not captured, resulting in poor understanding of patient knowledge regarding their family history of cancer. Objective: To assess knowledge of cancer-related family history for first- and second-degree relatives among an urban underserved patient population. Funding source: The American Cancer Society. Methods: University of Illinois Health patients aged 45-75 years without a history of colorectal cancer, who received an order for colorectal cancer screening through fecal immunochemical testing or screening colonoscopy were eligible to participate. A total of 88 respondents completed a 23-item telephone survey assessing knowledge of their family cancer health history using a 5-point Likert scale. Surveys were administered in both English and Spanish languages. Results: Of the 88 survey participants, 50 (57%) were female, 54 (61%) were of black or African American race, and 31 (36%) were of Hispanic or Latino ethnicity. On a single-item question assessing overall knowledge of their cancer-related family history, 35 (39.7%) responded they know it well or very well, versus 13 (14.8%) with little or no knowledge. On knowledge of maternal cancer related history, 8 participants (9.1%) reported little or no knowledge of their mother’s cancer history, and 29 participants (33%) reported little or no knowledge of their maternal relatives’ cancer history. On knowledge of their father’s cancer history, 35 (39.8%) reported little or no knowledge of their father’s cancer history, and 48 participants (54.5%) reported little or no knowledge of their paternal relatives’ cancer history. Conclusions: This original research study addresses the current gap in understanding patient knowledge regarding familial cancer health history. Survey results demonstrate a striking discrepancy between respondent reported overall knowledge of cancer-related family history, and knowledge of their maternal and paternal cancer histories. Moreover, respondents reported increased knowledge of their mother’s versus father’s cancer history p < 0.0001. Improved recognition of unknown family history in first- and second-degree family members may improve cancer-risk assessment.