This paper presents a framework that extends a partial evaluation method for transformational programs to a method for reactive CSP processes. Temporal logic formulas are used to represent constraints on the sets of the sequences of communication actions executed by the processes. We present a set of simple rules for specializing processes with temporal formulas which contain X(next)-operators and/or G(invariant)operators. We show the soundness of the rules. Our partial evaluation method specializes reactive processes with the specifications of their environments. Furthermore, we present an example of an application of our partial evaluation method to improve the security of concurrent systems..