Abstract Inoculation of lamb rotavirus to gnotobiotic lambs produced a disease characterized by diarrhoea and anorexia. Rotavirus was excreted in the faeces of the lambs for several days. One-day-old lambs were more susceptible than 12-day-old lambs. A serological response to infection was detected in all lambs by complement fixation and immunofluorescence techniques, using antigens prepared from calf rotavirus. Lamb rotavirus antiserum did not neutralize calf rotavirus, indicating the distinct nature of the lamb rotavirus. No evidence of latent infections was detected by treating the lambs with an immunosuppressant four months after initial recovery.