The authors describe CTDNet, a data-driven reduction machine for the concurrent execution of applicative functional programs in the form of lambda calculus expressions. Such programs are stored as binary-tree-structured process graphs in which all processes maintain pointers to their immediate neighbors (i.e. ancestor and two children). Processes are of two basic types: master processes, which represent the original process graph, and slave processes, which carry out the actual executional work and are dynamically created and destroyed. CTDNet uses a distributed eager evaluation scheme with a modification to evaluate conditional expressions lazily, together with a form of distributed string reduction with some graphlike modifications.