This study sets out to examine the ornamentation in the manu¬script GB-Cfm 32.G.29 (known as the Fitzwilliam Virginal Book) as representative of late sixteenth-century practice. The sixteenth- and early seventeenth-century ornamentation as practised on the Continent is also investigated, in order to elucidate the contemporary English practice, to evaluate it and place it in perspective. This period's concept of ornamentation is an ars diminutionis. The diminution technique (the breaking up of long note values into smaller ones) is expressed as passaggi (figurations) and ornaments, in order to provide a more elegant expression of the basic notes of a composition. Continental treatises describe the individual ornaments and thus provide a terminology with which to describe these ornaments. The ars diminutionis manifests itself in the FVB as written-out figuration, written-out ornaments and ornaments indicated by sign, the latter consisting of the single and double stroke which are peculiar to virginal music. No explanation for the Virginalists' signs exists, nor are contemporary English instruction books concerning themselves with keyboard ornamentation available. A comparison of the ornamentation of the manuscript with the printed edition of the FVB (1979-80), reveals many inaccuracies in the latter. These consist mainly of printer's errors, such as wrong placements and frequency of occurrence, which do not correlate with the original, and stenographic cancellation signs which are wrongly interpreted as ornaments. All of these are corrected in the present study. A collation of other source copies with the same pieces found in the FVB reveals many textual and ornamentation variants between them. Examining the written-out ornaments in the FVB, one finds that they are identical to the ornaments found in Continental sources. These ornaments are primarily employed as decoration of the individual closes in a cadence, where they occur as diminutions of the notes constituting the cadence. Here they are employed functionally, for example, to resolve the note of resolution in a discant close ornamentally, or to embellish the plain notes of a bass close. They are also used as virtuoso decoration as an intrinsic part of the passaggi, being diminutions of successive intervals. The single- and double-stroke ornament signs appear at first glance to be indiscriminately scattered over the music without purpose. Research into their use reveals them to be employed systematically, besides being decorative elements which add brilliance to the music. The frequency with which they coincide with the pulse unit and the rhythmic pulsation created by it, together with the profusion of their occurrence, make these signs a unique phenomenon in late sixteenth-century ornamentation. Their interpretation remains a difficult issue to clarify. The evidence assembled in this study points to a classification of the strokes according to the accenti e trilli principle. The single stroke can then be interpreted as a slide (from a third below the main note), and the double stroke as a tremolo or tremoletto - the most common sixteenth-century ornament. Its mirror-image, the mordent, is occasionally more appropriate in certain contexts, and in cadences the double stroke followed by a two-note suffix most likely signifies a groppo.