This thesis studies the ranks of secular clergy and their changing career patterns in the diocese of Hereford between 1400 and 1535. This diocesan study will contribute to the developing research of the late medieval English clergy. The printed episcopal registers of Hereford are examined as the major source for the present thesis. Other additional records, for example, the Valor Ecclesiasticus of 1535, are also introduced as supplementary evidence. The study consists of five aspects relating to the clerical career in the late medieval diocese of Hereford. The changing patterns of clerical recruitment during the studied period are analysed in virtue of the calculation of acolytes and priests which were included in the ordination lists. The clerical movement across the diocesan boundaries in the phase of ordination is demonstrated through the calculation of letters dimissory held by ordinands. Various titles presented by individuals during the ordinations are categorised and analysed to indicate the different economic resources in the early stage of a clerical career. The other two aspects concern clerical careers after the ordination. The admission to a benefice is discussed through the analysis of the exercise of patronage regarding the parochial advowsons held by various patrons. The actual economic status of a parochial incumbent on the eve of the Reformation is demonstrated by the information extracted from the Valor Ecclesiasticus. Based on the analyses of this thesis, the clerical career still had its attractiveness in the pre-Reformation diocese of Hereford, and secular clergy was a rank with the activeness and significance within the late medieval church and had close connections with the contemporary secular society.