The aim of this paper is to evaluate efficiency of different approaches to parallelization ofstiffness matrix assembly operations, that can be found in any finite element software. OpenMP [1, 2]and POSIX Threads (Pthreads) programming models are two considered in this paper. The OpenMPmodel consist of an Application Program Interface (API) for multi-platform shared-memory parallelprogramming in C/C++. POSIX is an acronym for Portable Operating System Interface and Pthreadsstandards [3] defined as a set of C/C++ language [4] programming types and procedure calls forshared-memory parallel programming. The paper shows that parallelization can efficiently exploit thepower of modern available hardware, significantly reducing the needed computation time. Differentapproaches of each programming model are used for parallelization of stiffness matrix assemblycompared and their efficiency is evaluated in this paper.The different parallelization strategies were implemented in OOFEM [5] which is a free finiteelement code with object oriented architecture for solving mechanical, transport and fluid mechanicsproblems that operates on various platforms. The finite element method leads to set of algebraic equa-tions which components are assembled from contributions of individual elements. In this paper wefocus on assembly of sparse matrix contributions, such as stiffness as mass matrices. Domain decom-position paradigm, where the whole domain is decomposed into sub domain, which contributions areevaluated and assembled by individual threads is hard.The paper discuss the differences between approaches based on OpenMP and Pthreads, datascoping specification for correct parallel programming and memory allocation synchronization andscheduling.