Personality and social relationships were assessed twice across a 4-year pe
riod in a general population sample of 489 German young adults. Two kinds o
f personality-relationship transaction were observed. First, mean-level cha
nge in personality toward maturity (e.g., increase in Conscientiousness and
decrease in Neuroticism) was moderated by the transition to partnership bu
t was independent of other developmental transitions. Second, individual di
fferences in personality traits predicted social relationships much better
than vice versa. Specifically, once initial correlations were controlled fo
r, Extraversion, Shyness, Neuroticism, self-esteem, and Agreeableness predi
cted change in various qualities of relationships (especially with friends
and colleagues), whereas only quality of relationships with preschool child
ren predicted later Extraversion and Neuroticism. Consequences for the tran
sactional view of personality in young adulthood are discussed.