This paper introduces a citation analysis study on the references of doctoral dissertations of organic chemistry in Peking University from 1995 to 1999. The sequence of the most often cited international journals is given. Among the total 2818 references, the Chinese literature counts for 13.2% and the foreign languages materials counts for 86.8%. Among the foreign language materials, the periodicals count for 92.7% in the whole cited foreign references. The statistics shows that twelve titles of foreign periodicals can meet half of the users' demands and if the satisfaction rate rises to 80%, the library needs to subscribe to more than 60 titles of foreign periodicals.