Carrier erythrocytes are used to disseminate drugs in the circulatory system of animals. Carrier erythrocytes prepared from white-tailed deer (Odocoileus virginianus) do not circulate well in vivo. Although carrier cells were prepared from sickle and non-sickle cells with no apparent differences, their 24-hour survival was only 10 per cent. Osmotic fragility of carrier cells was increased over that of normal deer erythrocytes. Unlike erythrocytes from other ruminants, deer carrier erythrocytes are extremely fragile. Scanning electron micrographs of deer erythrocytes (sickle or non-sickle) in different stages of carrier cell preparation revealed no morphological differences. These data suggest that carrier cells from deer would not be amenable for use in long-term dissemination of drugs.