The slave trade between Indian Ocean and Rio de la Plata, at the end of the XVIIIth century and at the beginning of the XIXth, braved numerous difficulties (tempests, wrecks, epidemics, wars). The documentation of the National Record Office of Buenos Aires shows how the risks were beforehand calculated, thanks to ingenious financial raisings that the slavetraders elaborated in the international places, in order to preserve a benefit performance and promote the progress of their activities.