  In stellar astrophysics, the study of the atmospheres of early-type stars
plays a very special role. The atmospheres of these stars display a variety of
different phenomena, such as the presence of large magnetic fields, strong
surface convection, pulsation, diffusion of chemical elements. In particular,
about 10% of early F-, A- and late B-type stars present chemical peculiarities,
which rise as a result of diffusion. A detailed study of the evolution of the
chemical peculiarities as traces of diffusion processes requires the precise
knowledge of stellar ages and initial chemical composition. Open clusters
provide these information: 1) it is possible to assume that all cluster members
have approximately the same original chemical composition and age; 2) the age
of stars belonging to open clusters can be determined with much higher accuracy
than for field stars. For this reason chemically peculiar stars member of open
clusters have been targeted to study the evolution of the chemical
peculiarities primarily to provide constraints to diffusion models. We review
the abundance studies of chemically peculiar stars in open clusters performed
until now, putting their results into the broader context of stellar evolution.
