During the last years numerous constructs have been proposed for concurrent programming. The relationship between a representative collection of such constructs is considered in the framework of transformational semantics. In particular procedure-oriented versions, where processes communicate via synchronized or protected access to shared memory, as well as message-oriented approaches, where processes communicate via message channels, are considered. The duality of these two concepts is outlined. Moreover these constructs are compared to applicative constructs for concurrent programming such as data flow languages.