A study was undertaken at the University of Liverpool to investigate the potential for using construction and demolition waste (C&DW) derived aggregate in the manufacture of precast concrete building blocks. Recycled aggregates can be used to replace quarried limestone aggregate, usually used in coarse (6 mm) and fine (4 mm-to-dust) gradings. Market research was carried out to determine the economic viability of using C&DW derived aggregates in blocks. The availability and transportation costs of quarried and C&DW derived aggregates were compared. Technical aspects, in addition to economic aspects, of the use of C&DW derived aggregates in block manufacture were investigated, especially in view of the effect of C&DW derived aggregate on compressive strength.