Optimal culture conditions in artificial nutritive media were determined for a defined avirulent strain of Treponema hyodysenteriae and for four field strains of treponemas in pigs with clinical dysentery. The treponemas were isolated with the use of milliporous filters with pores of 0.3 micrometer in diameter, which were located on the surface of blood agar. No significant difference in the influence of equine, bovine or sheep blood on the growth of treponemas was determined. The commercial amount of glucose in the used media, 2.0 to 2.5 g per 1,000 ml, was quite sufficient for the growth of the treponemas and it was not necessary to increase the amount. After reaching the optimal rate of growth the oxidoreduction potential was diminished by adding cystein or cystein hydrochloride and placing the Petri dishes with the media, prior to inoculation, into an anaerobic medium filled with hydrogen. The suitable composition of the culture atmosphere created in a special anaerostat comprised 0.4 to 1.0% carbon dioxide and the rest being hydrogen. Treponemas grew on the blood agar in zones with very slight hemolysis without forming separated colonies.