This work presents the development of a modular code for the dynamic simulation of a single-shaft gas turbine and an application to a 50 kW machine. The simulation package, CAMEL (R), is a modular object-oriented process simulator for energy conversion systems, conceived and developed in the last decade by the Authors' group at the Mechanical and Aeronautical Engineering Department of the University of Roma 1 "La Sapienza", the advantages of an object-oriented approach being the flexibility and the user-friendly interface. The component library of the original (steady-state) code has been augmented by implementing the dynamic models of all of the gas-turbine components: the method is still based on a classical black-box modelling and each component can be assembled as in an engineering process scheme in which the connections between two elements represent either a mechanical power coupling or a working fluid stream. In order to obtain an accurate description of the gas-turbine phenomenology, each component is described by a non/linear set of both algebraic and first-order differential-equations. The global non-linear system is advanced in time by means of a fourth-order Runge-Kutta method. The paper provides a description of the mathematical model adopted for the simulation. A complete dynamic simulation of a 50 kW gas-turbine plant is performed, starting from steady-state operation. Both variable and fixed rotational velocity are considered. The program has been tested both in a steady-state off-design simulation and in a fully dynamic simulation. In all tests the code performed properly, reproducing with good accuracy the behaviour of the real gas turbine. (C) 2007 Elsevier Ltd. All rights reserved.