Splitting tension tests of concrete block masonry specimens were used to investigate the in-plane tensile strength of concrete block masonry. The strength and geometric properties of the blocks and of various strength grouts were included as test parameters. Explanations for the observed behaviour were suggested. In addition to providing test data for evaluating current design provisions for tension produced by combinations of in-plane loads, documentation of the relative influence of grouting is an important objective of this paper. The results indicate inconsistencies with the current design assumption that grouted blockwork is equivalent to construction with solid units. Some general conclusions related to design provisions are provided.