Provided that Supersymmetry (SUSY) is realized, the Large Hadron Collider (LHC) and the future International Linear Collider (ILC) may provide a wealth of precise data from SUSY processes. An important task will be to extract the Lagrangian parameters. On this basis the goal is to uncover the underlying symmetry breaking mechanism from the measured observables. In order to determine the SUSY parameters, the program Fittino has been developed. It uses an iterative fitting technique and a Simulated Annealing algorithm to determine the SUSY parameters directly from the observables without any a priori knowledge of the parameters, using all available loop-corrections to masses and couplings. Simulated Annealing is implemented as a stable and efficient method for finding the optimal parameter values. The theoretical predictions can be provided from any program with SUSY Les Houches Accord interface. As fit result, a set of parameters including the full error matrix and two-dimensional uncertainty contours are obtained. Pull distributions can automatically be created and allow an independent cross-check of the fit results and possible systematic shifts in the parameter determination. A determination of the importance of the individual observables for the measurement of each parameter can be performed after the fit. A flexible user interface is implemented, allowing a wide range of different types of observables and a wide range of parameters to be used.Program title: FittinoCatalogue identifier: ADWNProgram summary URL: http://cpc.cs.qub.ac.uk/summaries/ADWNLicensing provisions: GNU General Public LicenseProgramming language: C++Computer: any computerOperating system: Linux and other Unix flavorsRAM: ca. 22 MBNo. of lines in distributed program, including test data, etc.: 111 962No. of bytes in distributed program, including test data, etc.: 1 006 727Distribution format: tar.gzNumber of processors used: 1External routines: The ROOT data analysis framework, the SPheno spectrum calculator (included in the distribution). (SPheno may be replaced by any SUSY code which makes predictions for observables and communicates via the SLHA.)Nature of problem: Provided supersymmetry is realized in Nature, a wealth of data will become available at the Large Hadron Collider (LHC) and the International Linear Collider (ILC). One of the most important tasks will be to extract the SUSY Lagrangian parameters from the measured observables. The large number of SUSY parameters and complicated correlations induced by loop corrections make the parameter determination difficult. Starting a global SUSY parameter fit initialized with tree-level estimates turned out to be an insufficient approach because the MINUIT fitting algorithm is likely to get stuck in local minima.Solution method: To overcome the encountered problems without using a priori knowledge, two strategies have been implemented in Fittino. The first one performs the fit in several steps (sub-sector fit method). It starts fitting certain sub-sets of parameters to certain sub-sets of observables and thereby slowly improves the parameter values. Finally the values are good enough to start a global SUSY parameter fit.The second approach uses simulated annealing to improve the tree-level estimates of the parameters to an extend where MINUIT succeeds to perform a global SUSY parameter fit.Restrictions: The current version of Fittino (version 1.1.1) assumes that there is no CP violation in the SUSY sector, no mixing between generations and no mixing within the first two generations.Running time: Depending on the complexity of the problem, the running time varies from a few minutes to several weeks.