Item 12(b). CERTIFICATION UNDER SECTION 906 OF SARBANES-OXLEY ACT OF 2002 Name of Issuer: T. Rowe Price Blue Chip Growth Fund In connection with the Report on Form N-CSR for the above named issuer, the undersigned hereby certifies, to the best of his knowledge, that: 1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; 2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Issuer. Date: February 18, 2005 /s/ James S. Riepe ---------------------------------- James S. Riepe Principal Executive Officer Date: February 18, 2005 /s/ Joseph A. Carrier ---------------------------------- Joseph A. Carrier Principal Financial Officer