A system for treating distinct batches of workpieces to serial procedures comprises first and second multi-site structures. In each multi-site structure the sites are rotatable for alignment in turn with loading and unloading stations together constituting treatment or process stations. Workpieces of a batch are loaded onto all of the treatment sites and then simultaneously and identically treated by operation of treatment stations with which the process sites are aligned. After treatment in the first structure, workpieces of a batch are transferred from the unloading stations of the first structure to the loading stations of the second structure for further processing.