Aplastic anemia in association with estrus was diagnosed in 6 pet ferrets. The ferrets had been examined because of anorexia, depression, and lethargy of 2-5 days' duration. Consistent clinical findings were pale mucous membranes and enlargement of the vulva. Hemorrhages were found in 3 ferrets. Hematologic findings included severe anemia, thrombocytopenia, granulocytopenia, and hypocellularity of the bone marrow. The aplastic anemia was attributed to prolonged estrogenic exposure in ferrets with protracted estrus.