This catalogue is based on the one that forms part of my doctoral dissertation. Its aim is to set down as complete a record of Howells's work as a composer as present information allows, always taking into account the possibility of new discoveries or new information about known works coming to light in the future. To that end, in addition to listing every complete published, performed and recorded work, it also includes entries for works for which there is some primary or secondary documentary evidence, but that are no longer extant, or are known or assumed to be missing. As in the earlier catalogue, Howells's works are arranged in chronological order so far as it is possible to be certain of the date of completion. But Howells was an artist who was far from consistent in his recording of these details on his manuscripts or elsewhere, and, for example, in cases where there was a gap sometimes of some years between composition and publication or performance, the date of a number of works has to be a best guess, based on all the available information. This relative uncertainty is reflected in some of the entries. In addition, as some works, including a few major compositions, were revised or added to over a considerable period of time or existed in more than one version (HH 61 and HH 111 are cases in point) the decision has been taken to assign the earliest date at which a viable version is known to have existed.