We propose a programming formalism that provides multiprocess synchronization and priorities. As in CCS and CSP, processes communicate by executing pairs of complementary actions. Processes are labelled transition systems, where the labels are formed by combining atomic actions with the operators Λ, ⌝. Intuitively, a Λ b expresses multiple synchronization on actions a,b, while ⌝e expresses that the actions specified by e cannot be performed in the current environment.