The subject of this study is Manuscript No 51 in the Archives o f the Cracow General Chapter. Although students of early liturgical drama and historians o f Roman liturgy got used to make references to it, the failed to note - which may adversely affect the value of their work - that their source had not been subjected to a full critical examination. This task has been undertaken by the author of this study. He offers a general description of the manuscript and its contents. In the non-illuminated manuscript he distinguishes an earlier text, produced in Olomouc by the end of the 13th century and a later text, written in Cracow. Close textual analysis reveals that it is an Ordinarium, and not, as it was erroneously assumed, an Antiphonale. The dating of the MS has been based on an examination of palaeographic and liturgical evidence (the former summed up in expert opinions). It is argued further that the use of Sanctorale as a reference frame in the interpretation of this MS leads to untanable conclusions and must be regarded as erroneous;there is a much better case for the use of the Temporale instead. Finally, the author addresses the issue of the provenance of the manuscript. He finds the liturgical argument crucial in dismissing the thesis that the codex was produced in Cracow. Of the eleven liturgical books that do come from Cracow only two missals display the motif of the blessing of bunches of twigs on Palm Sunday which is reminiscent of that scene in MS No 51. The topographical elements on p. 18v in all certainty refer to Olomouc; a clear indication that the MS must have been produced in the old capital of Moravia. All the researches conducted by the author support the conclusion that MS No 51 dates from the end of the 13 th century and should be identified as Ordinarium Olomucense in Cracovia. It seem s to have been used by one of the cantors to conduct the Divine Service in cathedral churches, first in Olomouc, then in Cracow.