The Polycomb-group constitutes an important, widely conserved group of tran
scriptional repressors best known for their function in stably maintaining
the inactive expression patterns of hey developmental regulators, including
homeotic genes. Together with the counteracting trithorax-group proteins,
they establish a form of cellular memory by faithfully maintaining transcri
ption states determined early in embryogenesis. Besides being crucial for t
he correct execution of developmental programs, Polycomb-group mediated sil
encing also appears to be involved in controlling cell proliferation. Here
we discuss several aspects of Pc-G function: target gene specificity and re
cognition as well as propagation of inactive chromatin states to subsequent
cell generations.