The two volume set LNCS 4051 and LNCS 4052 constitutes the refereed proceedings of the 33rd International Colloquium on Automata, Languages and Programming, ICALP 2006, held in Venice, Italy, in July 2006. The first volume (LNCS 4051) presents 61 revised full papers together with 1 invited lecture that were carefully reviewed and selected from 230 submissions…