This paper presents a general method for designing delay insensitive datapath circuits. Its emphasis is on the formal derivation of a circuit from its specification. We discuss the properties required in a code that is used to transmit data asynchronously, and we introduce such a code. We introduce a general method (in the form of a theorem) for distributing the evaluation of a function over a number of concurrent cells. This method requires that the code be "distributive." We apply the method to the familiar example of a ripple-carry adder, and we give a CMOS implementation of the adder.