Reactive extraction (in situ transesterification) of Jatropha curcas L (Jatropha) seeds for biodiesel production is influenced by a variety of parameters, including seeds size, agitation speed, reaction temperature, reaction time, catalyst concentration and molar ratio of alcohol compare to the oil. In this study, these parameters were studied in the ranges of <0.5-4 mm seeds particle size, 200-300 rpm, agitation speed, 30-60 degrees C reaction temperature, 10-60 min reaction time, 0.1-0.2 N NaOH concentration and 100-600 molar ratio of methanol-to-oil. It was established that the smallest particle size (below 0.71 mm) resulted in the highest yield of biodiesel production. The biodiesel yield was found to be independent of intensity of the mixing once it reached 300 rpm, whereas reaction temperature did not exhibit any significant effect on the yield. It was also demonstrated that alkaline reactive extraction was complete in 20-30 min. The concentration of NaOH can affect biodiesel yield in both positive and negative way. Low concentration of NaOH (0.05 N) resulted in low yield, but at higher concentrations (0.2 N), emulsions form, due to a saponification side reaction, adversely affecting the yield. In this case, a NaOH concentration of 0.15 N produced the highest yield. It was also discovered that when the methanol-to-oil ratio reached 400, the biodiesel yield reached a constant state. The optimal conditions in this study are approximately <0.71 mm seeds particle size, 300 rpm mixing speed, 30 degrees C reaction temperature, 30 min reaction time, 0.15 N NaOH concentration and methanol:oil molar ratio of 400. (C) 2011 Elsevier B.V. All rights reserved.