The Proceedings of the Third International Workshop on Very Large Floating Structures (VLFS'99) includes 110 written contributions by 241 authors on the Mobile Offshore Base Project of the U.S. and the Mega-Float Project of Japan, as well in the general areas related to the design and analysis of VLFS. The Workshop was held in September 22-24, 1999, Honolulu, and attended by more than 160 researchers from 10 countries.