The Merrill Lynch Puttable FLOATs/RITES Trust Series PT-623, Relating to Massachusetts Health and Educational Facilities Authority, Revenue Bonds, Massachusetts Institute of Technology Issue, Series K, are rated 'AAA/A-1'. The long-term component of the rating is based on the underlying bond. The short-term component of the rating is based on a liquidity LOC guarantee from Bayerische Hypo-und Vereinsbank AG, and the expiration date of the liquidity facility is March 15, 2003.