Optimization of the fermentation media for maximization of surfactin production was carried out. The carbon source (glucose), the nitrogen source (ammonium nitrate) and the mineral salts ferrous and manganous sulphates were the critical components of the medium optimized. A 2(4) full factorial central composite experimental design followed by multi-stage Monte-Carlo optimization was used in the design of experiments and in the analysis of results. This procedure limited the number of actual experiments performed while allowing for possible interactions between the four components. The optimum values for the tested variables for the maximal production of surfactin were (in g dm(-3)) : glucose = 36 . 5; NH4NO3 = 4 . 5; FeSO4 = 4 x 10(-3) and MnSO4 = 27 . 5 x 10(-2). Relative surfactant concentrations were expressed as the reciprocal of the critical micelle concentration (CMC(-1)) and the maximum predicted yield of surfactin in terms of CMC(-1) was 45 . 5.