This study evaluated the response and susceptibility of four lines of ring-necked pheasants to infection with marble spleen disease (MSD) virus. Fifteen birds of the following lines were used: the standard ring-necked gamebird, the highly inbred jumbo white, the Sichuan, and the first-generation cross of the Sichuan and the standard gamebird. Baseline immune responses were assessed at 6 weeks of age by lymphoblastogenesis assays. All birds were orally challenged at 7 weeks of age with cell -culture-propagated MSD virus. Eight birds of each group were necropsied at 6-7 days post-inoculation (PI), and gross splenic lesions were recorded. Appropriate tissue sections were collected, fixed in 10% buffered formalin, and routinely processed for microscopic evaluation. The remaining birds were bled weekly from week 2 through week 8 Pl. Serum was tested for antibodies to MSD virus using a commercial enzyme-linked immunosorbent assay kit. Results of the lymphoblastogenesis assays and the gross and microscopic lesion incidences indicated that variations did exist between several lines evaluated. The jumbo white pheasant had significantly higher lymphoblastogenesis stimulation index and was more resistant to developing gross and histologic lesions than was the standard ring-necked gamebird.