The production of Clostridium sordelli veterinary vaccine is prepared by culturing the microorganism in large industrial bioreactors and purifying the toxin from culture supernatants. Currently, the harvesting time is established as function of bacterial growth, but not always this moment is associated to the maximum concentration of toxin present in the supernatant. Thus, it is easy to find different total amounts of toxin produced batch to batch. Besides, at present the toxin concentration is measured by in vivo LD50 methods, and results can be obtained only after 72h, when the bioreactor was already stopped.Moreover, the method is labour intensive and requires the use of a significant number of experimental animals We describe the development of a latex agglutination reagent for semiquantification of Clostridium sordelli lethal toxin (TcsL) and its use in industrial bioreactors. The reagent was developed and characterized in our laboratory achieving a considerable low detection limit (8ng of toxin per ml of culture supernatant) and then it was validated in actual industrial conditions. The use of such a rapid (i.e, in minutes) and easy to use reagent will allowto followthe culture in real time and thus standardizing the optimal end-point for harvesting in terms of toxin quantity.As an immediate consequence, the efficiency of TcsL industrial production may be optimized.