Summary form only given. In natural language research, many (grammar) trees were felled in 1992, to make room for the highly successful string-based HMM industry. A small literature survived on parsing (putting a tree on a string) and syntactic language modeling (putting a weight on a string). However, trees are making a comeback. Tree transformations are turning out to be very useful in large-scale machine translation (MT), and we will cover recent developments in this area. Most of the tree techniques used in MT turn out to be generic, leading to tools and software for manipulating tree automata in general. Tree acceptors and transducers generalize HMM techniques to the world of trees, raising many interesting theoretical and practical problems.