The influence of sex, reproductive maturity, and parental experience on the behavior of Siberian hamsters (Phodopus sungorus sungorus) toward strange pups was examined in this study. Immature, mature, or parentally experienced male and female Siberian hamsters were presented with 3- to 8-day-old pups. We recorded pup carrying during the initial 10 min, nesting with pups after 8 or 14 h, and attacking pups during the test period. Among inexperienced animals, more mature males attacked pups than did immature males or mature females. Parental experience significantly decreased pup attacks by males and increased nesting with pups by both males and females. Repeated testing did not modify the responses to pups. We conclude that in Siberian hamsters both caretaking and aggressive responses to pups may be shown by immature and mature animals of both sexes. Parental experience resulted in increased caretaking by males and females and decreased aggressive responses by males.