Little information has been published concerning the timeliness of follow-up after abnormal mammography. This article presents data on follow-up after abnormal mammography, including differences in follow-up by age, race, mammographic interpretation, and type of tracking system. From unpublished data, the rate of timely follow-up 8 to 12 weeks after index abnormal mammography ranges from 69% to 99%. Women aged 65 and older, those of lower socioeconomic status, and those who are instructed to have repeat evaluations in four to six months have the highest proportion of untimely follow-up. With use of computer-based tracking systems, timely follow-up ranges from 89% to 99%. Computer-based tracking systems should be encouraged to promote timely follow-up of abnormal mammography. Further research is needed to better delineate those at risk for untimely follow-up after abnormal mammography, causes of untimely follow-up, the impact of untimely follow-up on breast cancer stage and mortality, and interventions that maximize timely follow-up.