The practical experience of parallelising a simulator of gen- eral scattering and radiation electromagnetic problems is presented. The simulator stems from an existing sequential simulator in the frequency domain and can be fruitfully used in applications such as the test of coverage of a wireless net- work, analysis of complex structures, and so on. After the analysis of a test case, two steps were carried out: firstly, a "hand-crafted" code parallelisation was developed within the kernel of the simulator. Secondly, the sequential library, used in the existing simulator, was replaced by the parallel MUMPS library in order to solve the associated linear al- gebra problem in parallel. For factorising the matrix with MUMPS, two different ordering methods have been consid- ered. Copyright © 2009 ICST.