Determinations were carried out for the effect of temperature, NaCl concentration and aeration of solutions on the survivability of stage II larvae of Contracaecum rudolphii nematode. Stage II larvae hatched from egg shells were placed in tap water as well as in 1% and 3% solutions of NaCl. Part of the culture was run on Petri dishes and aerated each day. The second part was transferred into high beakers and left non-aerated. All cultures were run in three replications at temperatures of 4, 10, 20 and 30 degrees C. Microscopic observations of the survivability and activity of the larvae were conducted every day in all samples. The larvae incubated for 30 days at a temperature of 4 degrees C were viable and non-motile. The longest life span was noted in the case of the larvae incubated in the aerated 1% solution of NaCl at a temperature of 10 degrees C, which also recorded the lowest mobility. The shortest life span was reported for the larvae incubated in the non-aerated 3% solution of NaCl at a temperature of 30 degrees C. The results obtained in this study indicate that the II stage larvae of C. rudolphii may live both in both fresh and salt waters and a significant factor determining their life span is water saturation with oxygen.