The susceptibility of Psammomys obesus (sand rat) and Meriones tristrami (Tristram's jird) to Neospora caninum was investigated by subcutaneous (s.c.) and intraperitoneal (i.p.) inoculation of 10-fold doses of culture-derived tachyzoites. Groups of 5 animals were inoculated with doses of 10–10⁷ parasites via each route of inoculation. All but 2 of the sand rats inoculated with doses of 10–10⁴ parasites succumbed to the infection by 7–18 days postinfection. All jirds inoculated with 10⁷ tachyzoites succumbed by 5–16 days postinfection and those inoculated with 10⁶ tachyzoites by 9–25 days. A considerable proportion of the jirds inoculated with 10–10⁵ tachyzoites survived. Fibrinous peritonitis with ascites containing numerous tachyzoites was observed in the i.p.-inoculated sand rats and jirds that succumbed to the infection. In the jirds, tachyzoites were also found in pleural exudate. A considerable number (42.8%) of the jirds inoculated s.c. or i.p. exhibited neuromuscular symptoms, expressed in ataxia, head tilt, circling movement, and posterior paralysis. Seven successive passage of tachyzoites were achieved in sand rats with doses of 10⁵ parasites and in jirds with doses of 10⁷ parasites. All surviving jirds became seroconverted and were immune to lethal challenge.