The effects of fermentation performance on the final production cost of poly(3-hydroxybutyrate) [P(3HB)] were examined. Two processes for the production of P(3HB) by Alcaligenes latus from sucrose with the recovery method of surfactant-hypochlorite digestion were designed and subsequently analysed. The actual fermentation results that were different in the final P(3HB) content, P(3HB) yield and P(3HB) productivity were used in the simulations. The production cost of P(3HB) was significantly lower with higher P(3HB) content due to the reduction in polymer recovery cost. The cost of raw materials (mainly sucrose) was also lower with higher P(3HB) content since the process yielding higher P(3HB) content also resulted in higher P(3HB) yield on carbon source. The direct fixed capital-dependent costs decreased with increasing productivity. By employing the fermentation process that resulted in high P(3HB) concentration, P(3HB) content and P(3HB) productivity of 98.7 g/l, 88.3% and 4.94 g P(3HB)/l/h, respectively, the final production cost of P(3HB) was as low as US $2.6/kg P(3HB). (C) 1998 Elsevier Science Limited. All rights reserved.