Microbial retting of sunhemp was carried out using various strains of Aspergillus niger and Bacillus subtilis. The effect of concentration of the microbial strains and the time of retting on the mechanical properties of the retted fibers was studied. The retting time was reduced from 7 or more days in water with naturally-occurring water microorganisms to 4 days with the known microbes in distilled water. The tensile strength of the fibers increased with an increase in the amount of inoculum up to a certain limit, after which it decreased. Thus, controlled microbial retting of sunhemp is a viable method for the production of fibers of greater tensile strength than those produced by the traditional method.