According to Scientific Style and Format [Council of Science Editors, Seventh Edition, 2006], meeting abstracts should be cited using the following format:
Author(s) of abstract. Title of abstract [abstract]. In: Name of conference or title of publication.; conference dates; place of conference. Place of publication: publisher; date of publication. Abstract number.
Li TW, Jones PA. Methylation changes in early embryonic genes in cancer [abstract]. In: Proceedings of the 97th Annual Meeting of the American Association for Cancer Research; 2006 Apr 1–5; Washington, DC. Philadelphia (PA): AACR; 2006. Abstract nr 30.