  Mixing in the D0 system may provide a sensitive probe for new physics beyond
the Standard Model (SM) but has so far eluded experimental observation. The SM
predictions are typically small (< 10^{-3}) for the mixing parameters x, y
which, in the absence of charge-parity (CP) symmetry violation, measure the
mass (x= Delta(m)/Gamma) and lifetime (y= Delta(Gamma)/2Gamma) difference of
the CP eigenstates in the D0 system. The asymmetric B-factory experiments BABAR
and Belle open up the opportunity of measuring x, y with unprecedented
statistical precision and sample purities. Results from BABAR and Belle, and
from CLEO are reviewed.
