To optimize the production of novel ketal compounds and allenic ethers from a man-rove fungus Xylaria sp. 2508, optimization of the culture medium was carried out using a two-step approach. A quick identification of a suitable source of carbon and nitrogen was obtained by a simple screening experiment, which was followed by an application of response surface methodology (RSM) for further optimization design. A second order model was found to fit the eucalyptene A production. Response surface analysis revealed that the optimum values of the tested variables for the production of eucalyptene A were: glucose 2.86% (w/v), peptone 0.78% (w/v) and yeast extract 0.35% (w/v). A production of 4.89 x 10(-7) g ml(-1) for eucalyptene A, which was close to the predicted response, was observed in verification experiment. The production of xyloketal A was 2.20 x 10(-7) g ml(-1). In comparison to their production of basal medium, 1.53- and 1.32-fold increase had been obtained, respectively. The 3-D response surface curves implied that high yeast extract concentration repressed the growth of Xylaria sp. (c) 2005 Elsevier Ltd. All rights reserved.