The genome-wide search for the prostate cancer gene holds the promise of the availability of prostate cancer susceptibility testing in the near future. When this occurs, self-reported history of prostate cancer will be critical in determining who is eligible for cancer susceptibility testing. Little attention has been given to the reliability of self-reported family history of prostate cancer, particularly in African American men. This correlational study measured the stability of self-reported family history of prostate cancer over a one-year time period (between 1997 and 1998) with 96 African American men from a southern state. The men were asked on two separate occasions, 1 year apart, "Have any of your men blood relatives ever had prostate cancer?" The question had a prior test-retest reliability of 0.85 over a 2-week period. Forty-eight percent of the men changed their answers on the second administration. Men most likely to change their answers were low-income men and men who did not participate in a free prostate cancer screening. This research highlights the need for public genetic education and the recognition by health professionals that self-reported family history of cancer is a variable that changes as families have increased awareness and communication concerning family history of cancer.