Blakeslea trispora (+) MTCC, Blakeslea trispora NRRL 2895 (+), Blakeslea trispora NRRL 2896 (-) as well as intraspecific mating of both the strain types have been studied for optimum production of P-carotene. Intraspecific mating of both the strain types increased the yield of P-carotene to a considerable level (98 2 mg/l) as compared to wild strains. Effect of different media components such as carbon, nitrogen, and sulphates, and that of process variables such as pH and inoculum size on P-carotene production by Blakeslea trispora in shake flask culture was investigated. One factor at-a-time method was employed for the optimization of media components. Response surface methodology (RSM) was further used to determine the optimum values of process variables for maximum P-carotene production. The fit of the quadratic model was found to be significant. A significant increase in P-carotene production (139 +/- 1 mg/l) was achieved using RSM. (c) 2007 Elsevier Ltd. All rights reserved.