Increased duration of cancer survival may allow a longer window for detection of metastases, including brain metastases. Using the entire population of Olmsted County, Minnesota, we looked at trends in the rate of brain metastases in people diagnosed with primary lung or breast cancers between January 1, 1988, and December 31, 2001. Yearly rates of brain metastases detection following the primary tumors were calculated from a combination of medical record and SEER database information. Trends in rates and gender differences were assessed. There was no discernible increase in the rates of brain metastases secondary to lung or breast cancer during the period of observation. However, women were twice as likely as men to have brain metastases detected following a primary lung cancer. This difference was constant over the time period. This twofold difference in brain metastases detected in women versus men with lung cancer deserves further evaluation and confirmation.