The production of the snail parasitic nematode  Rhabditis  sp. from Biomphalaria alexandrina and Lymnaea cailliaudi snails which were exposed to the nematode mixed with different concentrations of  the bacterial exotoxin Victoback₁₂ AS was studied  The maximum number of recovered nematodes was recorded for both Biomphalaria alexandrina and Lymnaea cailliaudi at the concentration of 10 I.S of nematode/snail  in 2% of Victoback₁₂ AS solution . The longest period of releasing nematodes was also recorded at the same concentration for both snail species. Thus this concentration is considered  the most suitable for field applications .