Ordered attributed grammars (OAGs) are extended for use on parallel computers. A partition of the attributes of a tree leads to parallel evaluation if each partition is taken care of by a separate process. Visit sequences for parallel ordered attribute grammars (POAGs) are constructed, and it is shown that the POAG class is of the same power as the OAG class. The construction always leads to deadlock-free attribute evaluators. The approach taken provides a uniform basis for a wide range of implementations on parallel computers, allowing fine-grain or coarse-grain parallelism, shared memory or distributed memory architectures, and synchronous or asynchronous communication. Several kinds of partitions are discussed, and some experimental results and experiences are described. >