if u r OPT expiring on 15 May-->Get I-20 for fall before July 15. if u r OPT expiring on 30 May-->Get I-20 for fall before July 30. if u r OPT expiring on 15 June-->Get I-20 for fall before August 15. if u r OPT expiring on 30 June-->Get I-20 for fall before August 30. if u r OPT expiring on 15 July or later date-->Get I-20 for fall. Condition: if you have I 20 for fall 2007, you could stay legally at US for 4 months (correct me if I am wrong) before your classes starts. Remarks: this is not a legal advise, for better advise, plz contact your international advisor.