We are interested in the stellar content in the central region
of active galaxies. In this aim, we perform stellar population synthesis
of the integrated starlight in the Optical and NIR using a mathematical
method (Pelat, 1997, MNRAS 284, 365) dedicated to the determination
of the best solution (among the many local solutions) in the stellar
population synthesis problem which is a complex inverse problem. A
new development of the code allows the determination of the error zone
around the solution, expected from the observational uncertainties. In
the next sections, we present this very powerful method and results
obtained from a sample of AGN.