The nematode Beddingia (Deladenus) siricidicola was introduced from Brazil, since it is the most effective biological control agent for the wood wasp, Sirex noctilio. In order to maintain its original characteristics through time, a protocol for the cryopreservation of this nematode was developed. The highest viability levels were obtained by incubating the nematodes, prior to immersion in liquid nitrogen, in 5% glycerol for several days until the suspension reached 60% glycerol. Viability was assessed 24 hours later by thawing the cryotubes in 37ëC tap water and immersing the opened cryotube in Ringer’s solution. The mean survival after storage was 73%.