Historians have overstated the role of adoption as a channel of upward social mobility for poor but bright young samurai in Tokugawa Japan. An analysis of family histories and public service records of four han shows that adoption helped to preserve both samurai lineages and the political system of daimyo rule. It also created opportunities for younger sons to remain in the elite class under a system of primogeniture. Adoption in the middle and upper (shi) ranks of the class was normally between related families of roughly the same social status. Where status differences were involved, the adopted son usually represented a higher status than the adopting family. The few records available for lower ranks (sotsu) reveal some marriage and adoption with commoners, but none with the higher ranks of the samurai class. In sum, adoption clearly supported the system of hereditary status, but rarely provided opportunities for poor but bright samurai to get ahead in society.