For industrial applications of our novel runaway-type vector for mammalian cell based on simian virus 40, we studied host range specificity of this vector, especially with human-derived cell lines, since human cells as hosts seem to be very important for the production of pharmaceuticals by genetic engineering. The runaway-type vector showed a high replication rate at a permissive temperature of 33 degrees C in HeLa cells and erythropoietin was produced effectively. The plasmid copy number was dependent on the temperature but was relatively low in KB cells. KB cells produced erythropoietin effectively at a non-permissive temperature of 37 degrees C despite the low plasmid copy number. On the other hand, neither runaway-type replication nor erythropoietin production was observed with blood cell derivatives such as HL-60 and RPMI-8226 cells.