Most of the current proposed routing protocols in Delay-Tolerant Network (DTN) are designed based on the entity mobility. In this paper, the authors consider the routing in DTN with group mobility, which is useful in modeling those cooperative activities. The new proposed routing scheme is called Group-Epidemic Routing (G-ER). G-ER is designed on the basis of one DTN protocol called Epidemic Routing (ER). In G-ER, two strategies related to the unique characteristics of the group mobility have been proposed to greatly improve ER. The first is to treat each group as a single node and exchange packets between groups instead of individual nodes.