In the course of the East Flanders Prospective Twin Survey (EFPTS), ha
ndedness was assessed as part of a genealogical study (Meulemans et al
., 1995) in 1616 twins (808 twin pairs) aged 6 to 28. Our findings are
that, in this large population-based study with known placentation an
d zygosity, the often observed higher frequency of left-handedness in
twins is confirmed, that it appears to he independent of zygosity and
chorion type, and that the belief that discordant handedness in monozy
gotic twins represents mirror-imaging is mythical.