What part does sexual orientation play in human development? Despite t
he apparent significance of sexual identities in shaping lives, develo
pmental research and theory on sexual orientation have, until recently
, been relatively limited. Today, as lesbian women, gay men, and bisex
ual people become more open about sexual identities, psychological kno
wledge about the ways in which developmental processes affect and in t
urn are affected by sexual orientation is growing rapidly. As the arti
cles in this special issue reveal, groundbreaking research is being co
nducted, from a variety of perspectives, by investigators from many di
fferent traditions. Research on sexual orientation and human developme
nt has the potential to make important contributions both to the theor
y and to the practice of developmental psychology.