The present studies examined beliefs concerning the impact of psychosocial factors in the transmission of contagious illness, injuries, and disgust. In Studies 1 and 2, participants ranging from preschoolers through adults judged the likelihood that a character would get sick (or injured) after being contaminated by another individual who was either of no stated relation to the character or who was a best friend, a disliked person, or a family member. Studies 3 and 4 examined effects of psychosocial relatedness on judgments of disgust (a psychological response). Study 5 examined the influence of germs on judgments of disgust. Overall, preschoolers through 2nd graders judged that any type of relatedness decreased the possibility of contracting illness from another person. However, for disgust, preschoolers judged that negative contagion would have a more powerful effect, particularly in the presence of germs. Relatedness had no effect on judgments of injury transmission. These results suggest that young children treat the psychological and biological domains as distinct but mutually interacting. (Contains 4 tables and 2 figures.)