1. The parasitic nematode Trichostrongylus colubriformis and free-living nematode Turbatrix aceti were examined for element content. 2. T. colubriformis contained significantly less phosphorus, potassium, manganese and boron than T. aceti. 3. T. colubriformis contained significantly more nitrogen and copper than T. aceti. 4. Comparative study of the chemical composition of parasitic vs free-living nematodes may facilitate in vitro cultivation of the parasitic forms.