This dissertation analyses the development of a Dublin bricklayers’ trade union, known officially after 1888 as the Ancient Guild of Incorporated Brick and Stonelayers' Trade Union, from its founding until 1921. This was one of the earliest Irish trade unions to come into existence, yet prior to this dissertation its multifarious character had never been thoroughly studied. Based upon extensive research into this union’s files, and into other sources of primary materials besides, the dissertation begins by examining the origins of the combination, and thereafter focuses upon its growth. The study offers a historical analysis, within the wider framework of the development of Irish trade unionism, of the evolution of a society of bricklayers from guild, to combination, and in 1888 to registered trade union. It is necessary to begin in 1670 in order to place the topic in its proper context. In that year the Guild of Bricklayers and Plasterers was established in Dublin by Royal Charter. It is argued here that the AGIBSTU can be looked upon as an offshoot of this guild, that is an organisational evolution from, rather than an organisational innovation upon, the guild. This is not a radical concept, however discovering a direct line of succession from a guild to a trade union is rare. The dissertation then concentrates primarily upon the evolution of the trade union within the period from 1869 to 1921. Various paramount aspects of the society within that timeframe are analysed thematically. This approach is adopted in order to chart, in detail, the development of what was, and would remain, a wholly Irish based trade union. The study also discusses the influence and impact of other trade unions, both Irish and British, and of social, political, and legislative developments, firstly upon the combination, and thereafter in greater depth, upon the trade union. It is argued that a sense of antiquity, nationalism, and a desire for hegemony over the bricklaying trade in Dublin, led the AGIBSTU to stand alone in its disputes, resolutely self-reliant.