Predicate expressions in a procedural programming language are based on sentences of predicate calculus of first order. The usage of predicate expressions in procedural languages leads to shorter, more effective and more readable programming code, and also decreases number of loops and local variables in procedures and programs. Predicate expressions in programming languages could be used with array, set and interval data types. Elements of array or set could be simple or complex data type. In this paper, definition and implementation of predicate expressions in procedural programming language Modula-2 is presented. Areas of usage are logic, set theory, graph theory, pattern recognition and others.