ABSTRACT: The specified concrete block masonry prism strengths in Table 4 of the CSA-S304-14 standard are known to be conservative. The values in this table, commonly used by designers as an alternative to testing, are becoming obstacles for concrete masonry construction in Alberta. Seven hollow and seven fully grouted three-course-high concrete block prisms (190 × 390 × 590 mm) were constructed from concrete blocks for each nominal strength of 10, 15, 20 and 30 MPa - 56 prisms in total. In order to obtain the compressive strength of the concrete masonry units, five concrete blocks were tested for each of the nominal strengths. The testing of the prisms followed the requirements of CSA-S304-14 and imposed a reduction of 9.47% to the measured compressive strength of the specimens when testing a three-coursehigh prism instead of a five-course-high prism. Three solid concrete prisms of the same dimensions as the three-course-high block prisms (190 × 390 × 590 mm) and three concrete cylinders (ϕ 100 × 200 mm) were also constructed for each concrete nominal strength of 15, 20 and 30 MPa for comparison. The results from the comparison between the compressive strengths of the concrete block prisms and solid concrete prisms and cylinders indicate the reduction factors required by the CSA-S304-14, but not by the CSAA23.1- 14, may be unnecessary. The experimental results suggest that two-course prism testing could be the standard test configuration for CSA-S304 as it is for the ASTM-C140 standard.