AbstractModern equation‐oriented simulators solve systems of equations and procedures using Newton's method or its variants. Partial derivatives of the output variables of procedures with respect to their input variables are required and are usually approximated by perturbation or quasi‐Newton methods. Here it is shown how this partial derivative information can be computed exactly for procedures in general, with particular applications to flash and multicomponent distillation procedures. Results indicate that 1. physical property procedures should provide analytical derivatives of properties in addition to point values; 2. commonly used procedures for vapor‐liquid equilibria calculation can easily be modified, and should be, to also return output/input gradients; and 3. the use of exact derivatives at all levels results in significant improvements in efficiency over present methods.