The present investigation was carried out to determine the core Non-Farsi periodicals of Molla Sadra Library in Shiraz University. The samples under study were 240 Non-Farsi periodicals published between 1995-2000 and 109 faculty members and researchers of the Faculty of Science.  The instruments used included a questionnaire, the periodicals left on the desks and the photocopied articles during a three-month period. The methodology used was bibliometrics. The core periodicals were determined using Bradford’s Law and the frequency of use of these periodicals. Furthermore, periodicals of any subject were ranked by the faculty instructors and finally, the core periodicals were compared with the ranked ones.  The findings indicated that instructors used periodicals more frequently (33 %) than the use they made of other information sources. The results also indicated that the existing stock of periodicals could only meet 19 percent of the instructors’ information needs. Molla Sadra Library’s performance was also considered to be satisfactory, since in 49 percent of the cases it could successfully provide the information inquirers with articles not available in the library. Another finding was that 69 percent of Non-Farsi periodicals were used with a frequency of lower than 10. The most frequently used periodicals constituted only 12.5 percent of the whole stock of periodicals and 45 percent of the periodicals had a maximum frequency of one. Moreover, 67 percent of the periodicals, ranked by the instructors, corresponded with the core periodicals resulted from Bradford’s Law.  Finally, the results indicated that from among the six faculty majors namely, Statistics, Mathematics, Geology, Biology, Physics and Chemistry, the periodicals related to Chemistry were used with the highest frequency. They were used in 4225 cases.