Five dogs with nonregenerative anemia were treated with human immunoglobulin as a 12-hour IV infusion, at dosages ranging from 0.5 to 1.5 g/kg of body weight. All dogs had a rapid response to treatment, with reticulocytosis within 1 to 4 days and a substantial increase in hematocrit within 3 to 8 days of treatment. In 2 of 5 dogs, the hematocrit returned to values within reference range and remained in the reference range for 8 to 14 months after treatment, despite discontinuing or tapering prednisone treatment to a low dose. In 3 of 5 dogs, the hematocrit did not return to the reference range. In 1 of these 3 dogs, the hematocrit remained at the new, increased value (26 to 28%) for 248 days after treatment, at which time the dog was euthanatized. In the other 2 dogs, the hematocrit had decreased to pretreatment values by 52 days after treatment. Retreatment of these 2 dogs resulted in a similar, but blunted, response to human immunoglobulin. Human immunoglobulin may be an effective treatment for some dogs with immune-mediated anemia that fail to respond to conventional treatment.